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Acknowledgments for DISCovering Science photos and images:

Aardvark: Young aardvark, photograph. Jen and Des Bartlett, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Abacus: Abacus, with Earth and Heaven beads, photograph Courtesy of Gale Research.
Abacus: Abacus, half of abacus with earth and heaven beads, photograph. Courtesy of Gale Research.
Abbe, Cleveland: Abbe, Cleveland, portrait. The Library of Congress.
Abbe, Ernst: Abbe, Ernst, photograph. The Library of Congress.
Abcess: Ameobic abcess, medicine, photograph. © Phototake (CN) /Phototake NYC. Reproduced with permission.
Abel, John Jacob: Abel, John Jacob, portrait. The Library of Congress.
Abel, Niels Henrik: Abel, Niels Henrik, portrait. The Library of Congress.
Accelerators: Mark I detector, photograph. © Lawrence Berkeley Lab, The National Audubon Society Collection/Photo Researchers, Inc.
Accelerators: Accelerators, charged particles. © Alexander Tsiaras, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Accelerators: Accelerators, portrait. The Library of Congress.
Accretion Disk: Cygnus X-1, black hole, phototgraph. © David Hardy/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Acid Rain: Acid rain damage, Chicago, photograph. JLM Visuals. Reproduced with permission.
Acidification (Acid rain): Forest, trees, frog, photograph. JLM Visuals. Reproduced with permission.
Acids & bases: Butanedioic acid, micrograph, photograph. © Astrid & Hanns-Frieder Michler/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Acne: Acne, young lady, photograph. © Biophoto Associates, Nation Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Acoustics: Acoustics, three figures illustrating acoustics, photograph. Courtesy of Gale Research.
Active galactic nuclei: Black hole, galaxy, photograph. © Mark Marten, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Acupuncture: Acupuncture, photograph. © Yoav Levy /Phototake NYC. Reproduced with permission.
Acupuncture: Acupuncture, side profile of head with pressure points, photograph. Hans & Cassidy. Courtesy of Gale Research.
Adaptation: Cactus plant, desert, photograph. JLM Visuals. Reproduced with permission.
Adaptation: Tall pine, forest, photograph. JLM Visuals. Reproduced with permission.
Addiction: Addiction, two men smoking crack, photograph. © Stock Market. Reproduced with permission.
Adenosine diphosphate: Adenosine diphosphate, chart representing cellular respirartion, photograph. Courtesy of Gale Research.
Adenosine triphosphate: Adenosine triphosphate, photograph. © M.W. Davidson, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Adhesive: Macrophotograph of adhesive, photograph. © Astrid & Hanns-Frieder Michler/Science Photo Library, The National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Adrenals: Cross section of human adenal gland, photograph. © artin M. Rotker/Phototake NYC. Reproduced with permission.
Adrian, Edgar Douglas: Adrian, Edgar Douglas, portrait. The Library of Congress.
Aerobic: Aerobic exercise, phtograph. © Dr. Tony Brain/Science Photo Library, National Audubon Society Colllection/Photo Resarchers, Inc.

Aerodynamics: Wind tunnel, photograph. © Dr. Gary Settles/Science Source, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Aerosol: (c) Chris Rogers, The Stock Market. Reproduced with permission.
Africa: Mount Kilmanjaro, photograph. JLM Visuals. Reproduced with permission.
Africa: Hans & Cassidy. Courtesy of Gale Research.

Africa: Africa, map, photograph. Courtesy of Gale Reaserch.
Agassiz, Jean Louis Rodolphe: Agassiz, Jean Louis Rodolphe, photograph. The Library of Congress.
Aging and death: Aging and death, two women, photograph. Custom Medical Stock Photo, Inc. Reproduced with permission.
Agouti: Agouti on hind legs, photograph. © Roy Pinney, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Agricultural machinery: Big red tractor, photograph. JLM Visuals. Reproduced with permission.
Agricultural machines: Agricultural machines, man plowing, photograph. © Ken Wagner/ Phototake NYC. Reproduced with permission.
Agrochemicals: Orchard sprayer, photograph. © Ken Wagner/Phototake NYC. Reproduced with permission.
Agronomy: Irrigated area, dry area, Iran, photograph. JLM Visuals. Reproduced with permission.
Aids: Mature virus, lymphocyte, photograph. © Scott Camazinr, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Air Pollution: Air pollution, smog over city, photograph. © Tom Carroll/Phototake NYC. Reproduced with permission.
Air pollution: Illustrations reprinted by permission of Robert L. Wolke.
Air pollution: Illustrations reprinted by permission of Robert L. Wolke.
Aircraft: Aircratf, stealth bomber, photograph. U. S. National Aeronautics and Space Administration (NASA).
Aircraft: Soviet Supersonic plane, photograph. U. S. National Aeronautics and Space Administration (NASA).
Aircraft: Voyager aircraft, portrait. The Library of Congress.
Airship: Santos Dumont airship, Paris, photograph. U. S. National Aeronautics and Space Administration (NASA).
Airship: Graf Zeppelin, portrait. The Library of Congress.

Airship: Airship, diagram, photograph. Hans & Cassidy. Courtesy of Gale Research.
Alaska Highway: Alaska Highway, photograph. © E. H. Cobb, U. S. Geological Survey.
Albatrosses: Waved albatross, photograph. JLM Visuals. Reproduced with permission.
Albedo: Albedo, photograph. © P. Carrara,U. S. Geological Survey.
Albinism: Albino negro with father, photograph. © Norman Lightfoot, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Alcohol: Alcohol, six molecular structures of various alcohols, photograph. Hans & Cassidy. Courtesy of Gale Research.
Aldehydes: Silver mirror test for aldehydes, photograph. © Jerry Mason/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Alder, Kurt: Alder, Kurt, portrait. The Library of Congress.
Alembert, Jean le Rond d': Alembert, Jean le Rond d', portrait. The Library of Congress.
Alexander, Archie Alphonso: Alexander, Archie Alphonso, (walking), photograph. Library of Congress.
Algae: green algae, photograph. © Rakoey, Alex/Custom Medical Stock Photo, Inc. Reproduced with permission.
Algae: Algae, flow chart, photograph. Hans & Cassidy. Courtesy of Gale Research.
Algal bloom: Ferraris, Greenpeace. Reproduced with permission.
Allergy: Allergy, flow chart, photograph. Hans & Cassidy. Courtesy of Gale Research.
Allergy: Hans & Cassidy. Courtesy of Gale Research.

Alluvial system: Crowsfoot delta, natural levee, photograph. © Dan Guravich, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Alternative energy sources: Wind generators, photograph. JLM Visuals. Reproduced with permission.
Alternative energy sources: Wind mill, photograph. The Library of Congress.
Alternative medicine: Doctor using acupuncture, photograph. Photograph by Charles Gupton. The Stock Market. Reproduced by permission.

Altimeter: Altimeter, balloon, line drawing. Han & Cassidy. Courtesy of Gale Research.
Aluminum: Illustrations reprinted by permission of Robert L. Wolke.
Aluminum: Aluminum, construction, photograph. JLM Visuals. Reproduced with permission.
Alzheimer's disease: Alzheimer's disease, brain tissue. © Cecil Fox/Science Source, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Amaranth: Amaranth, photograph. © Joe Munroe, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Amaranth: Amaranth, photograph. © 1992 Alan L. Detrick, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Amaryllis family: Amaryllis, photograph. © F. Gohier 1982, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Amaryllis family: Amaryllis, photograph. © Verna Johnston 1972, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
American alligator: M. Woodbridge Williams, National Park Service. Reproduced with permission.
Amino acid: Illustration. Robert L. Wolke. Reproduced with permission.
Amino acid: Amino acid, molecular structure of amino acid, photograph. Hans & Cassidy. Courtesy of Gale Research.
Amino acid (glycine): Glycine amino acid, computer graphic, photograph. © Scott Camazine, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Ammonia: Amonia molecule, photograph. © Ken Eward/Science Source, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Ammonification: Elk carcas, photograph. JLM Visuals. Reproduced with permission.
Amniocentesis: Amneocentesis, pregnant woman, photograph. © Will and Deni McIntyre, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Amphibians: Amphibians, flow chart, tadpole, frog, illustration. Hans & Cassidy. Courtesy of Gale Research.
Amplifier: Anteres fusion laser power amplifier, photograph. © Ray Nelson/PhototakeáNYC. Reproduced with permission.
Andersen, Dorothy: Andersen, Dorothy, portrait. The Library of Congress.
Anderson, Carl David: Anderson, Carl David, photograph. The Library of Congress.
Anesthesia: Ether, anaesthetic, photograph. © Jean-Loup Charmet, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Aneurism: Brain aneurism, photograph. © CNRI, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Aneurism: Aneurism, human brain, photograph. © Martin Rotker/Phototake NYC Reproduced with permission.
Angiography: Angiogram, coronary artery, photograph. © CNRI /Phototake NYC Reproduced with permission.
Angioplasty, balloon: Angioplasty balloon, photograph. © Will & Deni McIntyre, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Angioplasty, balloon: Angioplasty, balloon, line drawing. Hans & Cassidy. Courtesy of Gale Research.
Anglerfish: Angelrfish, photograph. JLM Visuals. Reproduced with permission.
Animal breeding: Cows, photograph. JLM Visuals. Reproduced with permission.
Anoles: Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Antarctica: Glacier System, Antarctica, photograph. JLM Visuals. Reproduced by permission.
Antarctica: Hans & Cassidy. Courtesy of Gale Research.

Antartica: Antartica, map, photograph. Hans&Cassidy. Courtesy of Gale Research.
Anteater: Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Antelopes and gazelles: Damaliscus Korrigon, photograph. © WM. J. Jahoda, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Antenna: Dopplar radar, photograph. Stock Market. Reproduced with permission.
Antibiotics: Penicillin culture. © McCarthy, T./ Custom Medical Stock Photo, Inc. Reproduced by permission.
Antibody and antigen: Antibody and antigen, two moleculer structures, photograph. Hans & Cassidy. Courtesy of Gale Research.
Antibody and Antigen: Antibody and antigen, molecular structure, photograph. Hans & Cassidy. Courtesy of Gale Research.
Antimony: Antimony, photograph. © Russ Lappa/Science Source, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Antisepsis:
Aphids: Peach aphid, photograph. © Dr. Jeremy Burgess/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Apollo 11, Spacecraft: Apollo 11 launch, photograph. U. S. National Aeronautics and Space Administration.
Appleton, Edward: Appleton, Edward, portrait. The Library of Congress.
Apraxia: Apraxia, brain, photograph. Hans & Cassidy. Courtesy of Gale Research.
Aquatic chemistry: National Center for Atmospheric Research/University Corporation for Atmospheric Research/National Science Foundation 539. Reproduced with permission.
Aqueduct: Roman aqueduct, Nimes, photograph. © John Moss, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Arachnid: Spider, photograph. JLM Visuals. Reproduced with permission.
Arachnids: Arachnid, web, photograph. JLM Visuals. Reproduced with permission.
Arago, Dominique Francois: Arago, Dominique Francois, portrait. The Library of Congress.
Arapaima: Arapaima gigas, photograph. © Steinhart Aquarium, Tom McHugh, Photo Researchers, Inc. Reproduced with permission
Arc: Hans & Cassidy. Arc, photograph. Courtesy of Gale Research.
Arch: Arch, line drawing. Courtesy of Gale Research.

Archaeology: Archaeological excavation, photograph. © Tom Bean/Stock Market. Reproduced with permissions.
Archaeology: Archeology, Montezuma castle, photograph. © Tom Bean/Stock Market. Reproduced with permission.
Archaeometallurgy: Research and Conservation Department, Florida Bureau of Archaeology. Reproduced with permission.
Archaeometallurgy: Research and Conservation Department, Florida Bureau of Archaeology. Reproduced with permission.
Archimedes: Archimedes, portrait. The Library of Congress.

Archimedes
Aristotle: Aristotle, portrait. The Library of Congress.

Armadillo: Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Armstrong, Edwin Howard: Armstrong, Edwin Howard, portrait. The Library of Congress.
Arrhenius, Svante August: Arrhenius, Svante August, portrait. The Library of Congress.
Arrow worms: Arrow worm , diagram, photograph. Hans & Cassidy. Courtesy of Gale Research.
Arrowroot: Arrowroot leaves on branch, photograph. © John Dudak/Phototake NYC. Reproduced with permission.
Arteriosclerosis: Carotid artery, photograph. © Alfred Pateka/CNRI/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Arteriosclerosis: Arteriosclerosis, flow chart, photograph. Hans & Cassidy. Courtesy of Gale Research.
Arthritis: Arthritis, deformed hand, photograph. © Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Arthritis: Arthritits, four illustrations of bone joints, photograph. Hans & Cassidy. Courtesy of Gale Research.
Arthropods: Chewing louse, photograph. JLM Visuals. Reproduced with permission.
Artifical fibers: Textiles, artificile fibers, photograph. Ted Horowitz/Stock Market. Reproduced with permission.
Artificial Fibers: Micrograph, polyester fibers., photograph. © Science Photo Library/National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Artificial Heart: Surgery, artificial heart, photograph. © NIH, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Arum family: Arum family, jack in pulpit, photograph. © Ted Keane, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Arum family: Arum family, skunk cabbage, photograph. © Roy Pinney, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Asbestos: JLM Visuals. Reproduced with permission.
Asexual reproduction: Salmonella cell dividing, asexual reproduction, photograph. © Dr. Kari Lounatimaa/ Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Asexual reproduction: Asexual reproduction, phases of mitosis, illustration. Hans & Cassidy. Courtesy of Gale Research.
Asia: Hans & Cassidy. Courtesy of Gale Research.

Assembly Line: Assembly line robot manufacturing Renault, France, photograph. © Cecilia Posada/Phototake NYC. Reproduced with permission.
Assimilative capacity: Assimilative capacity. Jill Beaumeister/Courtesy of U. S. Forest Service.
AST 1270: Torquetum, portrait. The Library of Congress.

AST 1270: Azimuth, portrait. The Library of Congress.

AST 1576: Cassiopeia constellation , portrait. The Library of Congress.
AST 1731: Hadley's sextant, portrait. The Library of Congress.
AST 1758: Halley's comet, portrait. The Library of Congress.
AST 1847: Mitchell, Maria , photograph. The Library of Congress.
AST 1888: Lick Observatory, portrait. The Library of Congress.
AST 1888: Lick Observatory, portrait. The Library of Congress.
Asthma: Hans & Cassidy. Courtesy of Gale Research.

Aston, Francis W.: Aston, Francis W., portrait. The Library of Congress.
Astroblemes: Large meteor crater, photograph. JLM Visuals. Reproduced with permission.
Astrolabe: Galileo's astrolab, photograph. © Archive, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Astrometry: Hubble Space Telescope, photograph. © NASA/ Mark Marten, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Astronauts: Tereshkova, Valentina, photograph. The Library of Congress.
Astronomists: Hubble, Edwin, photograph. The Library of Congress.
Astronomists: Kepler, Johannes, photograph of painting. The Library of Congress.
Astronomy: Astronomical device, portrait. The Library of Congress.
Astrophysics: Cartwheel galaxy, photograph. © Space Telescope Science Institute/ NASA/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Atmosphere, composition and structure of: Atmosphoer, line drawing. Hans & Cassidy. Courtesy of Gale Research.
Atmospheric circulation: Atmospheric circulation, photograph. National Center for Atmospheric Research/University Corporation for Atmospheric Research/National Science Foundation 532. Reproduced with permission.
Atmospheric observation: Atmospheric observation, photograph. National Center for Atmospheric Research/University Corporation for Atmospheric Research/National Science Foundation 221. Reproduced with permission.
Atmospheric Optical Phenomena: Sunset, sun dogs, frozen sea, photograph. © Dan Guravich 1987, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Atmospheric temperature: Satellite map of surface temperature, photograph. © Nasa/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Atmospheric temperature: Atmospheric temperature, graph, photograph. Hans & Cassidy. Courtesy of Gale Research.
Atmospheric temperature: Atmospheric temperature, graph of latitude and altitude, illustration. Hans & Cassidy. Courtesy of Gale Research.

Atmospheric temperature: Atmospheric temperature, graph, photograph. Hans & Cassidy. Courtesy of Gale Research.
Atom: Neon atom, computer generated model, photograph. © Kenneth Eward/BioGrafx, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Atomic bomb: Atomic bomb, portrait. The Library of Congress.
Atomic bombs: Atomic bombs, photograph. The Library of Congress.
Atomic Clock: Atomic clock, repairs, photograph. © Royal Greenwhich Observatory, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Atomic force microscope: Atomic force micrograph, photograph. © Philippe Plailly, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Atomic spectroscopy: Atomic spectroscopy, illustration of electrons during, photograph. Hans & Cassidy. Courtesy of Gale Research.
Atomic theory: Atomic theory, five circular illustrations, illustration. Hans & Cassidy. Courtesy of Gale Research.
Atomic theory: Three illustration of atomic theory, photograph. Hans & Cassidy. Courtesy of Gale Research.
Atoms: Illustration. Robert L. Wolke. Reproduced with permission.
Auk: Razorbills, rock, photograph. © Eric Hosking, F.R.P.S., National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Auroras: Northern lights display, photograph. © Pekka Parviatnen, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Australia: Australia, Mountains, photograph. JLM Visuals. Reproduced with permission.
Australia: Hans & Cassidy. Courtesy of Gale Research.

Australia: Hans & Cassidy. Courtesy of Gale Research.

Authors: Thoreau, Henry David (head and shoulders), drawing. The Library of Congress.
Automation: Large robotic machinery, photograph © Robert Essel/Stock Market. Reproduced with permission.
Automobile
Aye-aye: Aye-aye, photograph. © National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Baboon: Yellow baboon, photograph. © Malcolm Boulton, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Bacteria: Bacteria, microscopic image, photograph. JLM Visuals. Reproduced with permission.
Bacteria: Bacteria, diagram, phtograph. Hans & Cassidy. Courtesy of Gale Research.
Bacteriophage: Bacteriophage E-4, attacking Ecoli, photograph. © Lee D. Simon, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Bactian Camel: Camel, desert, photograph. © Paolo Koch , National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission

Badger: Badger, den hole, photograph. © Len Rue Jr., National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Baer, Karl Ernst von: Baer, Karl Ernst von, portrait. The Library of Congress.
Baeyer, Johann Friedrich Wilhelm Adolf von: Baeyer, Johann Friedrich Wilhelm Adolf von, portrait. The Library of Congress.
Bald eagle: Illustration. Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Bald Eagle: Bald eagles, photograph. © Vince Streano/Stock Market. Reproduced with permission.
Baldwin, Matthias: Baldwin, Matthias, portrait. The Library of Congress.
Balloon: Telescope, stratoscope II, photograph. U. S. National Aeronautics and Space Administration (NASA).
Balloon: Telescope, stratoscope II, photograph. U. S. National Aeronautics and Space Administration (NASA).
Balloon: Hot air balloon, photograph. © Paul Logsdon/Phototake NYC. Reproduced with permission.
Banana: Banana tree, photograph. © Irene Vandermolen, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Bandicoot: Cape York Bandicoot, Australia, photograph. © Jen and Des Bartlett, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Banting, Frederick G.: Banting, Frederick G., photograph. The Library of Congress.
Bar code: © Hammond Incorporated, Maplewood, New Jersey. Reproduced with permission.
Bar code: Bar code, line drawing. Hans & Cassidy. Courtesy of Gale Research.
Baranay, Robert: Baranay, Robert, portrait. The Library of Congress.
Barbiturates: Barbituates, illustration. Robert L. Wolke. Reproduced with permission.
Barkla, Charles Glover: Barkla, Charles Glover, portrait. The Library of Congress.
Barnacles: Goose Barnacles, photograph. JLM Visuals. Reproduced with permission.
Barnard, Christiaan Neethling: Barnard, Christiaan Neethling,áportrait. The Library of Congress.
Barometer: Barometer, photograph. © Diane Kalder/Bilderberg/Stock Market. Reproduced with permission.
Barracuda: Barracuda, photograph. © Ron Church, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Barrier Islands: Barrier Island, photograph. JLM Visuals. Reproduced with permission.
Bass: Bass swimming, photograph. © National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Bats: Bats in tree, photograph. © Don Mason/Stock Market. Reproduced with permission.
Bats: Bumblebee bat. © Bat Conservation International. Reproduced with permission.
Batteries: Collection of batteries, photograph. © Dr. Jeremy Burgess/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Battery: Battery, line drawing. Hans & Cassidy. Courtesy of Gale Research.
Battery: Battery, diagram, photograph. Hans&Cassidy. Courtesy of Gale Research.
Bear: Polar bear, photograph. © 1994 Zefa Germany/Stock Market. Reproduced with permission.
Bears: © U.S. Fish & Wildlife Service.
Beaver: Beaver, photograph. © Ron Sanford/Stock Market. Reproduced with permission.
Becquerel, Antoine-Henri: Becquerel, Antoine-Henri, portrait. The Library of Congress.
Bee-eaters: Bird eating a bee, photograph. © E. Hanumantha Rao, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Beech family: Chestnut tree, photograph. © Henry Mayer, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Beech family: Forest of beeches, photograph. © Pierre Berger, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Bees: Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Bees: Beehive on tree, photograph. JLM Visuals. Reproduced with permission.
Beet: Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Beetles: American carrion beetle, photograph. JLM Visuals. Reproduced with permission.
Begonia: Flowers, begonias, photograph. © A. Gurmankin 1987/Phototake NYC. Reproduced with permission.
Behavior: Behavior, bears in water, photograph. © Ron Sanford/Stock Market. Reproduced with permission.
Behring, Emil von: Behring, Emil von, portrait. The Library of Congress.
Bekesy, Georg von: Bekesy, Georg von, portrait. The Library of Congress.
Benz, Karl Friedrich: Benz, Karl Friedrich, portrait. The Library of Congress.
Benzene: Benzene molecule, computer graphic, photograph. © Ken Eward/Science Source, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Bergius, Friedrich: Bergius, Friedrich, portrait. The Library of Congress.
Berliner, Emile: Berliner, Emile, portrait. The Library of Congress.
Bernard, Claude: Bernard, Claude, portrait. The Library of Congress.
Bernoulli's principles: Charles D. Bernoulli's principles, young man blowing paper, photograph. © Charles D. Winters National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Berthelot, Pierre Eugene Marcellin: Berthelot, Pierre Eugene Marcellin, portrait. The Library of Congress.
Bessel, Friedrich: Bessel, Friedrich, portrait. The Library of Congress.
Bessemer, Henry: Bessemer, Henry, portrait. The Library of Congress.
Best, Charles Herbert: Best, Charles Herbert, photograph. The Library of Congress.
Big Bang: Big Bang, aftermath, photograph. © Ludek Pesek/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Binary Star: Binary star system, X-Ray, photograph. © Max-Planck-Institut Fur Physik Und Astrophysik, Science Photo Library. Reproduced with permission.
Binary star: Binary star, line drawing. Courtesy of Gale Research.
BIO 1542: Drawings of plants from De historia stirpium, by Leonhart Fuchs, portrait. The Library of Congress.
BIO 1607: Rhinoceros illustration based on an Albrecht Duerer drawing, portrait. The Library of Congress.
BIO 1625: A bee drawing from 17th century, portrait. The Library of Congress.
BIO 1665: Illustration from Robert Hooke's Micrographia, portrait. The Library of Congress.
BIO 1730: Frontispiece from 1904 ed . of John Bartram's Bartram's Garden, portrait. The Library of Congress.
BIO 1730: Illustration from 1904 ed . of Bartram's Garden, by John Bartram, portrait. The Library of Congress.
BIO 1730: Illustration from Jan Swammerdam's Bible of Nature, portrait. The Library of Congress.
BIO 1783: Illustration from 1907 edition of The Chinch Bug by F. M. Webster, portrait. The Library of Congress.
BIO 1803: Illustration from 1803 edition of Flora Boreali-Americana, portrait. The Library of Congress.
BIO 1827: Audubon watercolor of a golden eagle, portrait. The Library of Congress.
BIO 1866: Mendel, Gregor , portrait. The Library of Congress.
BIO 1908: Illustration of insects from U. S. Entomological Commission, portrait. The Library of Congress.
BIO 1914: Color drawing from a 1915 German science text, portrait. The Library of Congress.
BIO 1926: Magnus, Rudolf, portrait. The Library of Congress.
BIO 1928: Penfield, Wilder G., and Mrs., portrait. The Library of Congress.
BIO 1966: Choh-Hao, Li, portrait. The Library of Congress.

Biochemists: Seibert, Florence, photograph. The Library of Congress.
Biochemists: Tiselius, Arne Wilhel Kaurin, photograph. The Library of Congress.
Biochemists, Molecular Biologists: Szent-Gyorgyi, Albert, photograph. The Library of Congress.
Bioenergy: U. S. Department of Energy, Washington DC.

Biological Community: Mount Meadow, mule deer, Big Horn Mountains, photograph. JLM Visuals. Reproduced with permission.
Bioluminescenes: Lightning bug, photograph. © Roy Morsch/Stock Market. Reproduced with permission.
Biomagnification: Biomagnification, picture, photograph. Hans & Cassidy. Courtesy of Gale Research.
Biomass fuel: U. S. Department of Energy, Washington DC.

Biome: Boreal foest, Michigan, photograph. JLM Visuals. Reproduced with permission.
Biome: Turkey, Biome, photograph. JLM Visuals. Reproduced with permission.
Biome: Hans & Cassidy. Biome, chart, photograph. Courtesy of Gale Research.
Biophysicists: Crick, Francis, photograph. The Library of Congress.
Biophysicists: Yalow, Rosalyn S., photograph. The Library of Congress.
Biosphere: Robin Foster, Conservation International. Reproduced with permission.
Biot, Jean Baptiste: Biot, Jean Baptiste, portrait. The Library of Congress.
Biotechnology: Micro injection, foreign genes, photograph. © M. Baret/RAPHU, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Birch: Tall birch tree, photograph. © K. G. Vock/Okapia, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Bird of Paradise: Bird of Paradise, tree branch, photograph. © Tom McHugh, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Bird of paradise: Bird of paradise, Baiyer River Sanctuary, New Guinea © Tom McHugh, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Birdseye, Clarence: Birdseye, Clarence, portrait. The Library of Congress.
Birkeland, Kristian Olaf Bernhard: Birkeland, Kristian Olaf Bernhard, portrait. The Library of Congress.
Birth: Cow, Holstein giving birth, photograph. © Cynthia Matthews/Stock Market. Reproduced with permission.
Birth: Birth, baby's head emerging, photograph. © SIU, National Audubon Society Collection/ Photo Researchers, Inc. Reproduced with permission.

Birth: Birth, womb, baby, photograph. Hans & Cassidy. Courtesy of Gale Research.
Birth: Birth, baby in the womb, illustration. Hans & Cassidy. Courtesy of Gale Research.
Birth: Birth, expulsion of fetus, illustration. Hans & Cassidy. Courtesy of Gale Research.
Birth defects: Club foot, birth defects, photograph. © Science Source, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Bismuth: Bismuth crystals, photograph. © Earl Scott, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Bison: Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Bittern: Bittern, photograph. JLM Visuals. Reproduced with permission.
Bivalves: Bivalves, fish, photograph. Hans & Cassidy. Courtesy of Gale Research.
Black Hole Black Hole, photograph. U.S. National Aeronautics and Space Administration (NASA).
Black, Joseph: Black, Joseph, portrait. The Library of Congress.
Black Rhinoceros: Black rhinoceros, photograph. JLM Visuals. Reproduced with permission.
Blackbirds: photograph. Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Blackbirds: photograph. Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Blanchard, Thomas: Blanchard, Thomas, portrait. The Library of Congress.
Bleriot, Louis: Bleriot, Louis, portrait. The Library of Congress.
Blood: Red blood cells, walls of blood vessel. © Dennis Kunkel/Phototake NYC. Reproduced with permission.
Blood: illustration. Hans & Cassidy. Courtesy of Gale Research.
Blood gas analysis: Blood gas analysis, photograph. © Hank Morgan, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Blue revolution: Fisherman, net of fish, photograph. JLM Visuals. Reproduced with permission.
Bluebird: Mountain bluebird, flying, photograph. © Anthony Mercieca Photo, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Boas: Snake, Boa, photograph. © Stephen Green-Amitage/Stock Market. Reproduced with permission.
Bode, Johann Elert: Bode, Johann Elert, portrait. The Library of Congress.
Bond, chemical: Illustrations. Robert L. Wolke. Reproduced with permission.
Bond, chemical: Illustrations. Robert L. Wolke. Reproduced with permission.
Bond, chemical: Illustrations. Robert L. Wolke. Reproduced with permission.
Boobies and Gannets: Birds, Boobies, photograph. © Anthony Wolff/PhototakeáNYC. Reproduced with permission.
Boolean algebra: Boolean algebra, diagram, illustration. Hans & Cassidy. Courtesy of Gale Research.
Boolean algebra: Boolean algebra, diagram, photograph. Hans & Cassidy. Courtesy of Gale Research.
Boolean algebra: diagram. Hans & Cassidy. Courtesy of Gale Research.
Boolean algebra: diagram. Hans & Cassidy. Courtesy of Gale Research.
Boolean algebra: diagram. Hans & Cassidy. Courtesy of Gale Research.
Bordet, Jules: Bordet, Jules, portrait. The Library of Congress.
Boussingault, Jean-Baptiste Joseph: Boussingault, Jean-Baptiste Joseph Diellonne, portrait. The Library of Congress.
Bowerbird: Satin bowerbird, photograph. © Tom McHugh, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Boxfish: Male Pacific boxfish. © Fred McConnaughey, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Boyle, Robert: Boyle, Robert, photograph of painting. The Library of Congress.
Brachiopods: Brachiopod, diagram, photograph. Hans & Cassidy. Courtesy of Gale Research.
Brackish: Salt marsh, low tide NJ, photograph. JLM Visuals. Reproduced with permission.
Bragg, William Henry: Bragg, William Henry, portrait. The Library of Congress.
Brahe, Tycho: Brache, Tycho, photograph of painting. The Library of Congress.
Brain: Brain cells, microscopic image, photograph. © Prof. P. Motta/Dept. of Anatomy/University La Sapienza, Rome/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Brain: Brain, diagram, illustration. Hans & Cassidy. Courtesy of Gale Research.
Brattain, Walter Houser: Brattain, Walter Houser, portrait. The Library of Congress.
Brewing: Brewery, Dominican Republic, photograph. © John Olson/Stock Market. Reproduced with permission.
Brewster, David: Brewster, David, portrait. The Library of Congress.
Brick: Flat bed truck, bricks, photograph. JLM Visuals. Reproduced with permission.
Bridge: Bridge, Arizona, photograph. JLM Visuals. Reproduced with permission.
Bridge: Construction of bridge, Dame Point, photograph © Tom Carroll/Phototake NYC. Reproduced with permission.
Bridgman, Percy Williams: Bridgman, Pe rcy Williams, portrait. The Library of Congress.
Bromeliad: Spanish moss, photograph. © Maurice & Sally Landre, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Bromeliad: Moss, bromeliad, photograph. © Jack Dermid 1979, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Bromine: Vessel of bromine. © Charles D. Winters, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Brown pelican: photograph. Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Brown Pelican: Brown pelican, tree bark, photograph. JLM Visuals. Reproduced with permission.
Brown, Robert: Brown, Robert, portrait. The Library of Congress.
Bruce, David: Bruce, David, portrait. The Library of Congress.
Brunel, Isambard Kingdom: Brunel, Isambard Kingdom, portrait. The Library of Congress.
Bubonic Plague: Burning houses, bubonic plague, photograph. © St Bartholomew’s Hospital, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Buckland, William: Buckland, William, portrait. The Library of Congress.
Buckminsterfullerene: Chemical molecule, photograph. © J. Bernholc et al, North Carolina State University/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Buckwheat: White buckwheat, photograph. © John Kaprielian, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Buds and budding: Bacteria, budding hydra, photograph. © James Bell, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Building design/architecture: Contemporary architecture, photograph. JLM Visuals. Reproduced with permission.
Bunsen burner: Bunsen burner, photograph. © Yoav Levy/Phototake NYC. Reproduced with permission.
Bunsen, Robert: Bunsen, Robert, portrait. The Library of Congress.
Buoyancy: Man floating on back, water, photograph. JLM Visuals. Reproduced with permission.
Buoyancy: Principle of buoyancy. Hans & Cassidy. Courtesy of Gale Research.
Burbank, Luther: Burbank, Luther, portrait. The Library of Congress.
Burn: Burn, photograph. © Ann Chawatsky/Phototake. Reproduced with permission.
Bustard: Bustard in rift valley, photograph. © Mark Boulton, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Buttercup: Buttercups, photograph. © John Buitenkant 1993, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Butterflies: Butterflies, photograph. Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Butterflies: Butterflies, flow chart, life stages, illustration. Hans & Cassidy. Courtesy of Gale Research.
Butterflies: Butterflies, illustration. Hans & Cassidy. Courtesy of Gale Research.
Butterfly fish: Butterfly fish, photograph. JLM Visuals. Reproduced with permission.
Buzzard: Common buzzard, photograph. © H. Reinhard/Okapia, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Cactus: Cactus, photograph. Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Cactus: Cactus, photograph. Robert J. Huffman/Field Mark Publications.Reproduced with permission.
CAD/CAM: Computer CAD/CAM, photograph. © Ed Kashi/Phototake NYC. Reproduced with permission.
Caddisflies: Caddisflies, life stages, illustration. Hans & Cassidy. Courtesy of Gale Research.
Cadmium: Cadmium metal, photograph. © Rich Treptow, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Caffeine: Photograph. © Phillip A. Harrington, The Stock Market. Reproduced with permission.
Calcium carbonate: White cliffs, Dover, photograph. JLM Visuals. Reproduced with permission.
Calculator: Old and new calculators, photograph. © Doug Handel/Stock Market. Reproduced with permission.
Calculator: Calculator, babylonian digits, illustration. Hans & Cassidy. Courtesy of Gale Research.
Calculus: Calculus, graph approximating line segment, photograph. Hans & Cassidy. Courtesy of Gale Research.
Calculus: Calculus, graph, photograph. Hans & Cassidy. Courtesy of Gale Research.
California condor: Condor, photograph. © U.S. Fish & Wildlife Service.
Caliper: Caliper, measuring fat content, photograph. © Craig Hammell/Bikderberg Stock Market. Reproduced with permission.
Calorimetry: Calorimetry, illustration. Robert L. Wolke. Reproduced with permission.
Calorimetry: Calorimetry, glass of water, stirrer, thermometer photograph. Hans & Cassidy. Courtesy of Gale Research.
Calorimetry: Calorimetry, control panel, stirrer, photograph. Hans & Cassidy. Courtesy of Gale Research.
Calorimetry: Calorimetry, gerbil, photograph. Hans & Cassidy. Courtesy of Gale Research.
Calvin, Melvin: Calvin, Melvin, photograph. The Library of Congress.
Camels: Dromedary camel feeding, photograph. © Leonard Lee Rue, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Camels: Camel, photograph. JLM Visuals. Reproduced with permission.
Canal: Panama Canal, photograph. © Will & Demi McIntyre, National Audubon Society Collection/Photo Researchers, Inc. Reproduced by permission.
Canal: Canal boat, Netherlands, photograph. © Porterfield/Chickering, The National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Canal: Canal, line drawing. Courtesy of Gale Research.

Cancer: Cancer, micrograph, sarcona, photograph. © Dr. Brian Eyden, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Canines: Two hunting dingos, photograph. © Tom McHugh, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Canines: Canines, photograph. © U.S. Fish & Wildlife Service.
Capacitor: Electric fields, capacitor, photograph. © Yoav Levy/ Phototake NYC Reproduced with permission.
Captive breeding and reintroduction: Black-footed ferret, photograph. © Alan D. Carey, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Capuchin monkeys: White-fronted capuchin, photograph. © Renee Lynn, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Capybara: Capybara, photograph. Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Carbohydrate: Fructose molecule, computer diagram, photograph. © Chemical Design Ltd./Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Carbon: Carbon, illustration. Robert L. Wolke. Reproduced with permission.
Carbon: Carbon, illustration. Robert L. Wolke. Reproduced with permission.
Carbon: Carbon, illustration. Robert L. Wolke. Reproduced with permission.
Carbon: Gems, diamond raw form, photograph. © Rick Gayle/Stock Market. Reproduced with permission.
Carbon cycle: Carbon cycle ,outdoors, illustration. Hans & Cassidy. Courtesy of Gale Research.
Carbon dioxide: Jar containing dry ice, carbon dioxide, photograph. © R. Folwell, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Carbon monoxide: Carbon monoxide, graph, effects under exposure, illustration. Hans & Cassidy. Courtesy of Gale Research.
Cardano, Girolamo: Cardano, Girolamo, portrait. The Library of Congress.
Cardinals and grosbeaks: Cardinals and grosbeaks, photograph. Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Cardinals and grosbeaks: Cardinal, R. Cardinalus, photograph. JLM Visuals. Reproduced with permission.
Caribou: Caribou standing in forest, photograph. © Karl H. Maslowski, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Carnivore: Lion, photograph. JLM Visuals. Reproduced with permission.
Carnivorous plants: plant, photograph. Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Carnivorous plants: plant, photograph. Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Carnivorous plants: Venus flytrap, photograph. © Jerome Wexler 1981, National Audubon Society Collection/Photo Researchers Inc. Reproduced with permission.
Carnot, Nicolas-Leonard Sadi: Carnot, Nicolas-Leonard Sadi, portrait. The Library of Congress.
Carp: Carp, aqaurium, photograph. © Y. Lanceau Jacana, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Carrel, Alexis: Carrel, Alexis, portrait. The Library of Congress.
Carrot family: Cow parsnip and beach rose, photograph. © Mary M. Thatcher, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Carrot family: Carrot plant, leaves, photograph. © Hans Reinhard/Okapia 1990, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Carrying capacity: Carrying capacity. Courtesy of U. S. Forest Service.
Cartesian Coordinate Plane: Cartesian plane, line graph, photograph. Hans & Cassidy. Courtesy of Gale Research.
Cartesian Coordinate Plane: Cartesian Plane, graph, illustration. Hans & Cassidy. Courtesy of Gale Research.
Cartesian Coordinate Plane: Cartesian coordinate plane, graph, illustration. Hans & Cassidy. Courtesy of Gale Research.
Cartesian Coordinate Plane: Cartesian Plane, graph with triangle, photograph. Hans & Cassidy. Courtesy of Gale Research.
Cartography: Cartography, photograph. © M. R. Klepper/U. S. Geological Survey Photographic Library Denver, CO.
Cartwright, Edmund: Cartwright, Edmund, portrait. The Library of Congress.
Carver, George Washington: Carver, George Washington, portrait. The Library of Congress.
Cashew family: Cashew family, poison ivy, photograph. © Carolina Biological Supply/Phototake NYC. Reproduced with permission.
Cashew family: Pistachio tree, photograph. © Holt Studios International, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
CAT Scan: X-Rays, CAT scan, photograph. © Joseph Nettis, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Catfish: Brown Bullhead, photograph. JLM Visuals. Reproduced with permission.
Catheters: Cardiac catheterization, photograph. © Simon Fraser/Freeman Hospital, Newcastle-Upon-Tyne/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Cathode ray tube: Cathode ray tube, portrait. The Library of Congress.
Cats: Cats, Lynx, photograph. © Thomas H. Brakerfield/Stock Market. Reproduced with permission.
Cats: Two cheetahs, photograph. © Masud Quraishy, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Cattails: Cattails in field, photograph. © C. G. Maxwell, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Cattle: Water Buffalo, photograph. © George Turner, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Cattle Family: Longhorn cattle, photograph. JLM Visuals. Reproduced with permission.
Cauchy, Augustin-Louis: Cauchy, Augustin-Louis, portrait. The Library of Congress.
Cauterization: Birthmark cauterization, photograph. © Alexander Tsiaras, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Cave: Natural entrance, cave, photograph. JLM Visuals. Reproduced with permission.
Cavendish, Henry: Cavendish, Henry, photograph of painting. The Library of Congress.
Caves: Caves, stalactities and stalacmites, photograph. © Pedro Coll/Stock Market. Reproduced with permission.
Cayley, Arthur: Cayley, Arthur, portrait. The Library of Congress.
Celestial Coordinates: Polar equatorial star trails, photograph. JLM Visuals. Reproduced with permission.
Celestial Mechanics: Satellite, space mechanics, photograph. © Frank Rossotto/Stock Market. Reproduced with permission.
Cell: The living cell, photograph. © Fawcett, National Audubon Society Collection/ Photo Researchers, Inc. Reproduced with permission.
Cell: Cell, large diagram, photograph. Hans & Cassidy. Courtesy of Gale Research.
Cellulose: Cellulose, two diagrams, photograph. Hans & Cassidy. Courtesy of Gale Research.
Centipedes: Centipedes, photograph. JLM Visuals. Reproduced with permission.
Centrifuge: Centrifuge, phootograph. © Charles D. Winters, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
CERCLA: CERCLA, photograph. Robert Visser, Greenpeace. Reproduced with permission.
Cetaceans: Atlantic bottle-nose dolphin, photograph. JLM Visuals. Reproduced with permission.
Chain, Ernst Boris: Chain, Ernst Boris, photograph. The Library of Congress.
Chamberlain, Owen: Chamberlain, Owen, portrait. The Library of Congress.
Chameleon: Chameleon, photograph. JLM Visuals. Reproduced with permission.
Chaos: Dipolar vortices, collision, photograph. © G. Van Heijst and J. Flor, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Charles, Jacques-Alexandre-Cesar: Charles, Jacques-Alexandre-Cesar, portrait. The Library of Congress.
CHE 1100: 13th century Greek machines, portrait. The Library of Congress.
CHE 1540: Illustration of technique for separating metals from ores, portrait. The Library of Congress.
CHE 1548: Palissy crockery, photograph. The Library of Congress.
CHE 1548: Palissy crockery, photograph. The Library of Congress.
CHE 1548: Palissy the Huguenot Potter, photograph. The Library of Congress.
CHE 1669: Becher, Johann Joachim, photograph. The Library of Congress.
CHE 1669: German chemists, photograph. The Library of Congress.
CHE 1740: Primitive English chemistry lab, photograph. The Library of Congress.
CHE 1765: Scheelf, Karl Wilhelm, photograph. The Library of Congress.
CHE 1782: Instruments from Lavoisier's lab, photograph. The Library of Congress.
CHE 1782: Lavoisier, portrait. The Library of Congress.

CHE 1815: De Changy electric lamp for miners, photograph. The Library of Congress.
CHE 1823: 19th century chemistry lecture, photograph. The Library of Congress.
CHE 1823: Faraday, Michael, portrait. The Library of Congress.
CHE 1836: Constant battery, photograph. The Library of Congress.
CHE 1841: Chemical Society of London members, 1841, photograph. The Library of Congress.
CHE 1843: Chemical Society of London members, photograph. The Library of Congress.
CHE 1855: 19th century Bunsen burner, photograph. The Library of Congress.
CHE 1866: Rendition of benzol, photograph. The Library of Congress.
CHE 1869: Early Periodic Table, photograph. The Library of Congress.
CHE 1869: Manufacture of celluloid, photograph. The Library of Congress.
CHE 1911: Cellophane, photograph. The Library of Congress.

CHE 1911: Constitution of matter, photograph. The Library of Congress.
CHE 1913: Stainless steel cutlery, photograph. The Library of Congress.
CHE 1921: Midgley, Thomas Jr., portrait. The Library of Congress.
CHE 1934: Beckman, Arnold O., portrait
CHE 1940: Kamen, Martin D., portrait. The Library of Congress.
CHE 1952: Waksman, Selman A., portrait. The Library of Congress.
CHE 1954: Salk, Jonas, portrait. The Library of Congress.

CHE 1957: Bovet, Daniel, portrait. The Library of Congress.
CHE 775: Geber, portrait. The Library of Congress.
Cheetah: Cheetah, photograph. Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Chemical Warfare: Chemical warfare. © The Bettman Archive. Reproduced with permission.
Chemistry: Molecular graphics, photograph. © Ken Eward/BioGrafx/Science Source, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Chemistry: Chemistry, photograph. The Library of Congress.

Chemists: Davy, Humphry, photograph. The Library of Congress.
Chemists: Todd, Alexander Robertus, photograph. The Library of Congress.
Chemists, Microbiologists: Brown, Rachel Fuller and Elizabeth Lee Hazen, photograph. The Library of Congress.
Chemists, Physicists: Curie, Marie, photograph. The Library of Congress.
Chemists, Physicists: Curie, Pierre, photograph of painting. The Library of Congress.
Chemists, Physicists: Dalton, John, photograph of painting. The Library of Congress.
Chemists, Physicists: Faraday, Michael, photograph of sketch. The Library of Congress.
Chemists, Scientists: Langmuir, Irving, photograph. The Library of Congress.
Chemists, Scientists: Lavoisier, Antoine-Laurent, photograph. The Library of Congress.
Chemoreception: Chemoreception, photograph. © Carolina Biological Supp/Phototake NYC. Reproduced with permission.
Cherenkov, Pavel A.: Cherenkov, Pavel A., portrait. The Library of Congress.
Chevreul, Michel Eugene: Chevreul, Michel Eugene, portrait. The Library of Congress.
Chicken pox: Chicken pox, young girl, photograph. © Jim Selby/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Chimpanzee: Gorillas, photograph. © Kennan Ward/Stock Market. Reproduced with permission.
Chinchilla: Chinchilla, photograph. © National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Chipmunk: Chipmunk, photograph. JLM Visuals. Reproduced with permission.
Chlorine: Chemical reaction, sodium, chlorine, photograph. © Yoav Levy/Phototake NYC Reproduced with permission.
Chloroplast: Tobacco leaf chloroplast, micrograph, photograph. © Dr. Jeremy Burgess/Science Photo Library, National Audubon Society Collection/ Photo Researchers, Inc. Reproduced with permission.
Chocolate: Chocolate, line drawing. Courtesy of Gale Research.
Chocolate: Chocolate, chart, formed into chocolate bar, photograph. Hans & Cassidy. Courtesy of Gale Research.
Cholera: Vibrio Cholreae, choler, photograph. © McCarthy, T./ Custom Medical Stock Photo, Inc. Reproduced with permission.
Cholesterol: Monohydrate cholesterol crystals, photograph. © Dr. Jeremy Burgess/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Chromatography: Man with pharmaceutical machinery, photograph. © Simon Fraser/Searle Pharmaceuticals, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Chromium: Chemistry, chromium, photograph. © Yoav Levy/Phototake NYC Reproduced with permission.
Chromosomal abnormalities: Chromosomal abnormalities, two diagrams, illustration. Hans & Cassidy. Courtesy of Gale Research.
Chromosomal abnormalities: Chromosomal abnormalities, "X" and "Y" combinations, illustration. Hans & Cassidy. Courtesy of Gale Research.
Chromosomal abnormalities: Chromosomal abnormalities, chart, photograph. Hans & Cassidy. Courtesy of Gale Research.
Chromosome: X-chromosomes, reproductive chromosomes, photograph. © Biophoto Associates, National Audubon Society Collection/ Photo Researchers, Inc. Reproduced with permission.
Chromosome: Chromosome abnormalities, box with chromosomes, photograph. Hans & Cassidy. Courtesy of Gale Research.
Chromosome: Chromosome, illustrations, illustration. Hans & Cassidy. Courtesy of Gale Research.
Cicada: Cicada, human hand, photoograph. © Jen and Des Bartlett, National Aububon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Cigarette Smoke: Smoker's lung, normal lung, comparison, photograph. © A. Glauberman, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Circulatory system: Circulatory system, photograph. © Stock Market. Reproduced with permission.
Circulatory system: Circulatory system, line drawing. Hans & Cassidy. Courtesy of Gale Research.
Cirrhosis: Micrograph of liver cirrhosis, photograph. © Prof. P. Motta/Dept. of Anatomy/University of "La Sapienza", Rome/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
CITES: CITES, photograph. Haroldo Castro, Conservation International. Reproduced with permission.
Citric acid: Microscopic image of citric acid, photograph. © Alfred Pasieka/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Citric acid: Citric acid, molecular structure, photograph. Hans & Cassidy. Courtesy of Gale Research.
Citrus tree: Grapefruits, photograph. © 1980 Ken Brate, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Citrus trees: Citrus trees, photograph. © Scott Camazine, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Civets: Banded palm civet, photograph. © Tom McHugh, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Clausius, Rudolf Julius Emmanuel: Clausius, Rudolf Julius Emmanuel, portrait. The Library of Congress.
Clean Air Act: Clean Air Act, photograph. © Robert Visser, Greenpeace. Reproduced with permission.
Clean Water Act: Clean Water Act, photograph. Yuen-Gi Yee/U. S. Forest Service. Reproduced with permission.
Climax (ecological): Climax pine forest, photograph. JLM Visuals. Reproduced with permission.
Clone and cloning: Bannana plants, cloning. © Phillip Hayson, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Closed curves: Closed curves, six shapes, illustration. Hans & Cassidy. Courtesy of Gale Research.
Closed curves: Closed curve, figure eight shape, illustration. Hans & Cassidy. Courtesy of Gale Research.
Closed curves: Closed curve, drawing, illustration. Hans & Cassidy. Courtesy of Gale Research.
Closed curves: Closed curve, swirl, photograph. Hans & Cassidy. Courtesy of Gale Research.
Clouds: Cirrus, cumulus clouds, photograph. © John Deeks, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Clouds: One lane road, corn fields, photograph. JLM Visuals. Reproduced with permission.
Clouds: Clouds on a board. National Oceanic and Atmospheric Administration. Reproduced with permission.
Coal Seam: Coal Seam, CO., photograph. JLM Visuals. Reproduced with permission.
Coast and Beach: Long Island, South Fork, photograph. © Claudia Parks/Stock Market. Reproduced with permission.
Coast and beach: Coast, photograph. Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Coast and Beach: Lake, forest in background, photograph. © Al Greene and Associates, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Coati: Coati, photograph. © Leonard Lee Rue III, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Cobalt: Cobalt, photograph. © Russ Lappa/Science Source, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Coca: Leaves and fruit of coca plant, photograph. © Gregory G. Dimijian 1990, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Cocaine: Cocaine, plant, drugs, photgraph. Hans & Cassidy. Courtesy of Gale Research.
Cockatoos: Bird, cockatoos. © David Woods/Stock Market. Reproduced with permissions.
Cockcroft, John D.: Cockcroft, John D., photograph. The Library of Congress.
Cod: Black cod, photograph. © Zefa Germany/Stock Market. Reproduced with permissions.
Coelacanth: Coelacanth, photograph. © Planet Earth. Reproduced with permissions.
Coffee: Coffee, chart, beans into drink, photograph. Hans&Cassidy. Courtesy of Gale Research.
Coffee plant: Coffee tree, photograph. © Alan D. Carey, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Coffee plant: Coffee plant, line drawing. Hans & Cassidy. Courtesy of Gale Research.
Cogeneration: Cogeneration, photograph. © Robert Visser, Greenpeace. Reproduced with permission.
Cognition: Cognition, children, young boy playing. © Peter Saloutos/Stock Market. Reproduced with permission.
Colloid: Two bottles with light passing through them, photograph. © Charles D. Winters, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Colobus Monkey: Colobus monkey, photograph. © Tim Davis, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Color: Array of bright colors, photograph. © Thierry Cariou/Stock Market. Reproduced with permission.
Colorado River: Grand Canyon, ariel view of Colorado River, photograph. © Jeff Adamo/Stock Market. Reproduced with permission.
Coma: Coma, brain, causes, photograph. Hans & Cassidy. Courtesy of Gale Research.
Coma: Coma, illustration. Hans & Cassidy. Courtesy of Gale Research.
Combine harvester: Combine harvester, line drawing. Hans & Cassidy. Courtesy of Gale Research.
Combine harvester: Combine harvester, line drawing. Hans & Cassidy. Courtesy of Gale Research.
Combine harvester: Combine harvester, diagram of combine harvester, photograph. Hans & Cassidy. Courtesy of Gale Research.
Combustion: Chemistry combustion, photograph. © Yoav Levy/Phototake NYC. Reproduced with permission.
Comet: Comet West, 1976, photograph. U. S. National Aeronautics and Space Administration (NASA).
COMM 1878: Telephone, photograph. The Library of Congress.

COMP 1951: Computers, photograph. The Library of Congress.

Compact disc: Compact disc, photograph. IBM Almaden. Reproduced by permission.
Compass: Compass, line drawing. Hans & Cassidy. Courtesy of Gale Research.
Complex numbers: Complex numbers figure, graph, photograph. Hans & Cassidy. Courtesy of Gale Research.
Complex numbers: Complex numbers figure, acute angle, illustration. Hans & Cassidy. Courtesy of Gale Research.
Composite family: Composite family, photograph. Robert J. Huffman/Field Mark Publications. Reproduced by permission.
Composite family: Two blossoming artichokes, photograph. © 1983 Lawrence Midgale, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Composite family: Composite family, goldenrod flower, photograph. © John Dudak/Phototake NYC. Reproduced with permission.
Composting: Composting, photograph. Robert J. Huffman/Field Mark Publications. Reproduced by permission.
Compound chemical: Compound chemical, photograph. Robert L. Wolke. Reproduced by permission.
Compound chemical: Compound chemical, photograph. Robert L. Wolke. Reproduced by permission.
Compton, Arthur Holly: Compton, Arthur Holly, portrait. The Library of Congress.
Computer, Digital: Bit-serial optical computer, photograph. © David Parker, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Computer, digital: Computer mainframe, portrait. The Library of Congress.
Concrete: Concrete, photograph. Bridge support beams, photograph. David Pollack/Bikderberg, Stock Market. Reproduced with permission.
Concrete: Road construction paving, photograph. © Chris Jones/Stock Market. Reproduced with permission.
Concrete: Concrete, line drawing. Hans & Cassidy. Courtesy of Gale Research.
Concrete: Concrete, line drawing. Hans & Cassidy. Courtesy of Gale Research.
Concrete: Cement, preparing Portland cement, photograph. Hans & Cassidy. Courtesy of Gale Research.
Conditioning: Conditioning, children, photograph. © Elizabeth Hathon/Stock Market. Reproduced with permission.
Condor: California condor, rock, photograph. © Carl Koford, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Congruence (triangle): Congruence figures, triangles, photograph. Hans & Cassidy. Courtesy of Gale Research.
Congruence (triangle): Congruence figures, photograph. Hans & Cassidy. Courtesy of Gale Research.
Congruence (triangle): Congruence figures, ladder, photograph. Hans & Cassidy. Courtesy of Gale Research.
Congruence (triangle): Congruence figure, open triangle, photograph. Hans & Cassidy. Courtesy of Gale Research.
Congruence (triangle): Congruence figure, triangle open at side, photograph. Hans & Cassidy. Courtesy of Gale Research.
Conic sections: Conic section figure, cone, photograph. Hans & Cassidy. Courtesy of Gale Research.
Conic sections: Conic section, cone and circle, photograph. Hans & Cassidy. Courtesy of Gale Research.
Conic sections: Conic sections, cone and oval, photograph. Hans & Cassidy. Courtesy of Gale Research.
Conic sections: Conic sections, cone and arch, photograph. Hans & Cassidy. Courtesy of Gale Research.
Conic sections: Conic sections, photograph. Hans & Cassidy. Courtesy of Gale Research.
Conic sections: Conic sections, diagrams, illustration. Hans & Cassidy. Courtesy of Gale Research.
Conic sections: Conic sections, four large diagrams, photograph. Hans & Cassidy. Courtesy of Gale Research.
Conic sections: Conic sections, line drawing. Hans & Cassidy. Courtesy of Gale Research.
Conic sections: Conic sections, illustration. Hans & Cassidy. Courtesy of Gale Research.
Conic sections: Conic sections, illustration. Hans & Cassidy. Courtesy of Gale Research.
Conic sections: Conic sections, illustration. Hans & Cassidy. Courtesy of Gale Research.
Conic sections: Conic sections, illustration. Hans & Cassidy. Courtesy of Gale Research.
Conifer: Conifer, photograph. Robert J. Huffman/Field Mark Publications. Reproduced by permission.
Conifer: Conifer, photograph. Robert J. Huffman/Field Mark Publications. Reproduced by permission.
Connective tissue: Cartilage, photograph. © Prof. P. Motta/Dept. of Anatomy/University "La Sapienza", Rome/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Conservation: Radio collar on elk, photograph. JLM Visuals. Reproduced with permission.
Conservation laws: Conservation laws, two rockets, photograph. Hans & Cassidy. Courtesy of Gale Research.
Conservation laws: Conservation laws, bullet, momentum, photograph. Hans & Cassidy. Courtesy of Gale Research.
Conservation laws: Conservation laws, illustration. Hans & Cassidy. Courtesy of Gale Research.
Constellation: Constellation, Orion, photograph.. U.S. National Aeronautics and Space Administration (NASA).
Constructions: Construction, two merged circles with triangle in the middle, illustration. Hans & Cassidy. Courtesy of Gale Research.

Constructions: Construction, half circle and triangle, photograph. Hans & Cassidy. Courtesy of Gale Research.
Contaminated soil: Contaminated soil, photograph. U. S. Department of Energy, Washington DC.
Contamination: Contamination, photograph. © Neville Gaggiani/U.. S. Geological Survey Photographic Library Denver, CO.
Continental Drift: Continental Drift, illustration. Hans & Cassidy. Courtesy of Gale Research.
Continuity: Continuity, graph. Hans & Cassidy. Courtesy of Gale Research.
Continuity: Continuity, graph, photograph. Hans & Cassidy. Courtesy of Gale Research.
Continuity: Continuity, graph, illustration. Hans & Cassidy. Courtesy of Gale Research.
Continuity: Continuity, graph, photograph. Hans & Cassidy. Courtesy of Gale Research.
Contour Plowing: Contour framing, rice, photograph. © Paul Logsdon/Phototake NYC. Reproduced with permission.
Contraception: Contraceptives, photograph. © Michael Keller/The Stock Market. Reproduced with permission.
Convention on the Prevention of Marine Pollution: Convention on the Prevention of Marine Pollution, photograph. Hewetson, Greenpeace. Reproduced by permission.
Cooper, Peter: Cooper, Peter, portrait. The Library of Congress.
Coordination compound: Coordination compound, three illustrations, photograph. Hans & Cassidy. Courtesy of Gale Research.
Coordination compound: Coordination compound, equation, illustration. Hans & Cassidy. Courtesy of Gale Research.
Coordination compound: Coordination compound, electrons, photograph. Hans & Cassidy. Courtesy of Gale Research.
Coordination compound: Coordination compound,hybridization, photograph. Hans & Cassidy. Courtesy of Gale Research.
Coordination compound: Coordination compound,formation of chelated ring, photograph. Hans & Cassidy. Courtesy of Gale Research.
Coordination compound: Coordination compound, ethylenediamine tetraacetic, photograph. Hans & Cassidy. Courtesy of Gale Research.

Coordination compound: Coordination compound, molecular structure of metallo porphyrin units, photograph. Hans & Cassidy. Courtesy of Gale Research.
Copepoda: Crustacea Copepoda diaptomus, photograph. © M. I. Walker/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc Reproduced with permission.
Copernicus, Nicholas: Copernicus, Nicholas, photograph. The Library of Congress.
Copper: Copper, photograph. JLM Visuals. Reproduced with permission.
Coral Reef: Belau Kayangel atoll, photograph. © Douglas Faulkner, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Corals: Orange cup coral, photograph. JLM Visuals. Reproduced with permission.
Corals: Corals, diagram of insides, photograph. Hans & Cassidy. Courtesy of Gale Research.
Cori, Carl Ferdinand and Getty T.: Cori, Carl Ferdinand, Cori, Getty T., portrait. The Library of Congress.
Corliss, George Henry: Corliss, George Henry, portrait. The Library of Congress.
Cormorants: Cormorants, photograph. Robert J. Huffman/Field Mark Publications. Reproduced by permission.
Cormorants and Shags: Cormorants and shags, photogrpah. Robert J. Huffman/Field Mark Publications. Reproduced by permission.
Cosmic Rays: Cosmic Ray, photograph. © Prof. D. Skobeltzn, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Cotingas: Cotingas, photograph. © A.W. Ambler , National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Cotton: Cotton, fields, photograph. JLM Visuals. Reproduced with permission.
Cournand, Andre F.: Cournand, Andre F., portrait. The Library of Congress.
Courtship: Courtship, male peacock mating ritual, photograph. © Norbert Wu/Stock Market. Reproduced with permission.
Crab: Hermit crab, photograph. © Thomas Dimock/Stock Market. Reproduced with permissions.
Cram, Donald J.: Cram, Donald J., portrait. The Library of Congress.
Cranes: Bridge, laying decking, photograph. © Holt Confer/Phototake NYC. Reproduced with permission.
Cranes: Cranes, photograph. Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Cranes: Crowned crane, photograph. JLM Visuals. Reproduced with permission.
Cranes: Harbor, Washington Monument, portrait. The Library of Congress.
Crayfish: Crayfish, photograph. Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Cretaceous catastrophe: Cretaceous catastrophe, line drawing. Courtesy of Gale Research.
Crick, Francis: Crick, Francis, photograph. The Library of Congress.
Crocodiles: Crocodiles, photograph. © Planet Earth. Reproduced with permission.
Crocodiles: Tomistoma, photograph. © National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Crompton, Samuel: Crompton, Samuel, portrait. The Library of Congress.
Crop Rotation: Gas well, wheat and rice fields, photograph. JLM Visuals. Reproduced with permission.
Crowned Lemur: Crowned Lemurs, photograph. © National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Crows and jays: Crows and jays, photograph. Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Crustacea: Horseshoe crab, crustacea, photograph. © Diamon T. Smithers, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Cryogenics: Cryotubes, photograph. © Geoff Tompkinson, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Crystal: Crystal, photograph. Robert L. Wolke. Reproduced with permission.
Crystal: Pyrite crystal, photograph. © Joe Bator/Stock Market. Reproduced with permission.
Cuckoos: Roadrunner, photograph. © Allan D. Cruickshank, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Currents: Wave crests, photograph. JLM Visuals. Reproduced with permission.
Curve: Curve, three examples, photograph. Hans & Cassidy. Courtesy of Gale Research.
Cushing, Harvey Williams: Cushing, Harvey Williams, portrait. The Library of Congress.
Cushing's Syndrome: Cushing's syndrome, photograph. © John Radcliff Hospital/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Cuttlefish: Cuttlefish, photograph. © Fred McConnaughey, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Cuvier, Georges Leopold: Cuvier, Georges Leopold, photograph. The Library of Congress.
Cycad: Cycad, photograph. JLM Visuals. Reproduced with permission.
Cyclotron: Cyclotron, photograph. © Lawrence Berkeley Laboratory/ Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Cyclotron: Cyclotron, photograph. The Library of Congress.

Cystic Fibrosis: Cystic Fibrosis, physiotherapist helping young girl, photograph. © Simon Fraser, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Dacron: Dacoron polyester fibers, photograph. © Science Photo Library, The National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Daimler, Gottlieb: Daimler, Gottlieb, portrait. The Library of Congress.
Dam: Hoover Dam, photograph. © Roy Morsch/Stock Market. Reproduced with permission.
Dam: Dam, portrait. The Library of Congress.
Dama Gazelle: Dama Gazelle, photograph. © Mark Newman/Phototake NYC Reproduced with permission.
Damselflies: Damselflies, photograph. Robert J. Huffman/Field Mark Publications. Reproduced by permission.
Damselflies: Damselflies, photograph. © Charles Kreb/Stock Market. Reproduced with permission.
Dark Matter: Dark matter evidence, photograph. U.S. National Aeronautics and Space Administration (NASA).
Dating techniques: Tree growth rings, photograph. © Charles Krebs/Stock Market. Reproduced with permission.
Davisson, Clinton: Davisson, Clinton, portrait. The Library of Congress.
DDT: DDT, photograph. The Library of Congress.
DDT (Dichlorodiphenyl-trichloroacetic): DDT, photograph. © James P. Blair/National Geographic Image Collection. Reproduced by permission.
de Graaf, Regnior: de Graaf, Regnior, portrait. The Library of Congress.
de Vries, Hugo: de Vries, Hugo, (seated with legs crossed), photograph. The Library of Congress.
Debye, Peter: Debye, Peter, portrait. The Library of Congress.
Deer: Deer, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced by permission.
Deer: Deer, photograph. © Tom Brakerfield/Stock Market. Reproduced with permission.
DeForest, Lee: DeForest, Lee, portrait. The Library of Congress.
Deforestation: Jungle erosion, photograph. © Ulrike Welsch, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Delbruck, Max: Delbruck, Max, photograph. The Library of Congress.
Dementia: Coloured positron emission Tomo-acids, photograph. © Dept. of Nuclear Medinice, Charing Cross Hopital, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Democritus: Democritus, portrait. The Library of Congress.

Density: Water density, photograph. © Yoav Levy/ Phototake NYC Reproduced with permission.
Dental drill: Dental drill, photograph. © Randy Duchaine/The Stock Market. Reproduced by permission.
Dentistry: Dentist examining computerized X-rays, phototgraph. © National Institute of Health/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced by permission.
Dentistry: Denistry, tooths, photograph. Hans & Cassidy. Courtesy of Gale Research.
Deoxyribonucleic Acid (DNA): Structure of the DNA molecule, illustration. Robert L. Wolke. Reproduced by permission.
Deoxyribonucleic acid (DNA): DNA blueprint, photograph. © Phillippe Plailly/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Deposits: Large deposite site, photograph. JLM Visuals. Reproduced with permission.
Depression: Two false colored brains, photograph. © NIH/Science Source, National Audubon Society Collection/ Photo Researchers, Inc. Reproduced with permission.
Depth perception: Perception, baby grabbing object, photograph. © Gabe Palmer/Stock Market. Reproduced with permission.
Derivative: Derivitive figure, shaded graph, photograph. Hans & Cassidy. Courtesy of Gale Research.
Derivative: Derivitive figure, graph, upward sloping line, photograph. Hans & Cassidy. Courtesy of Gale Research.
Derivative: Derivitive figure, small graph, three lines, photograph. Hans & Cassidy. Courtesy of Gale Research.
Descartes, Rene: Descartes, Rene, photograph. The Library of Congress.
Desert: Sonoran Desert, Organ Pipe National Monument, photograph. © Robert Jureit/Stock Market. Reproduced with permission.
Desert: Desert, photograph. JLM Visuals. Reproduced with permission.
Desert tortoise: Desert tortoise, photograph. © U.S. Fish & Wildlife Service.
Determinants: Determinants, graph, photograph. Hans & Cassidy. Courtesy of Gale Research.
Determinants: Determinants, graph and equation, illustration. Hans & Cassidy. Courtesy of Gale Research.
Determinants: Determinants, six small boxes, photograph. Hans & Cassidy. Courtesy of Gale Research.
Determinants: Determinants, four small boxes, variables in corners, photograph. Hans & Cassidy. Courtesy of Gale Research.
Dewar, Sir James: Dewar, Sir James, portrait. The Library of Congress.
Diabetes Mellitus: Diabetes mellitus, photograph. © Dr. P. Marazzi/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Diagnosis: Diagnosis, doctor examining X-rays, photograph. Photograph by Randy Duchaine. Stock Market. Reproduced with permission.
Dialysis: Man on dialysis machine, photograph. © Giovaux Communication/Phototake NYC Reproduced with permission.
Diels, Otto: Diels, Otto, photograph. The Library of Congress.
Diesel engine: Diesel engine, graph, photograph. Hans & Cassidy. Courtesy of Gale Research.
Diesel engine: Diesel engine, four sketches, illustration. Hans & Cassidy. Courtesy of Gale Research.
Diesel, Rudolf Christian Karl: Diesel, Rudolf Christian Karl, portrait. The Library of Congress.
Diffraction: Color diffraction, photograph. © Peter Angelo Simon/Stock Market. Reproduced with permission.
Diffraction Grating: Circular diffraction pattern, photograph. © James Stevenson, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Diffusion: Carbon dioxide diffusion, photograph. © Andrew Mcclenaghan, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Diffusion: Diffusion, red blood cell, photograph. Hans & Cassidy. Courtesy of Gale Research.
Digestive system: Digestive system, diagram, human, photograph. Hans & Cassidy. Courtesy of Gale Research.
Dik Dik: Dik dik, photograph. © Rapho, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Dinosaur: Dinosaur imprint, photograph. JLM Visual. Reproduced with permission.
Dinosaur: Dinosaur bones, Thailand, photograph. © Bill Wassman/Stock Market. Reproduced with permissions.
Diode: Light enitted diode, photograph. © Yoav Levy/Phototake NYC. Reproduced with permission.
Dioxin: Dioxin, photograph. © Randy Lantz, Greenpeace. Reproduced with permission.
Dioxin: Dioxin, photograph. © Zachary Singer, Greenpeace. Reproduced with permission.
Dipole: Dipole, attraction between two xenon atoms, illustration. Hans & Cassidy. Courtesy of Gale Research.
Dipole: Dipole, molecular shape, illustration. Hans & Cassidy. Courtesy of Gale Research.
Dirac, Paul: Dirac, Paul, photograph of sketch. The Library of Congress.
Discoverers: Newton, Isaac, photograph of the painting. The Library of Congress.
Dissociation: Dissociation, volcano, photograph. © David Taylor, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Dissociation: Dissociation, positive, negative ions, water dipole, photograph. Hans & Cassidy. Courtesy of Gale Research.
Distance: Distance, graph, photograph. Hans & Cassidy. Courtesy of Gale Research.
Distance: Distance, graph with triangle, photograph. Hans & Cassidy. Courtesy of Gale Research.
Distillation: Distillation, apparatus, photograph. Hans & Cassidy. Courtesy of Gale Research.
Distillation: Distillation, illustration. Hans & Cassidy. Courtesy of Gale Research.
Dobzhansky, Theodosius: Dobzhansky, Theodosius, photograph. The Library of Congress.
Dogwood tree: Dogwood tree, photograph. JLM Visuals. Reproduced with permission.
Doisy, Edward A.: Doisy, Edward A., photograph. The Library of Congress.
Domagk, Gerhard: Domagk, Gerhard, portrait. The Library of Congress.
Dome: Cathedral dome, photograph. JLM Visuals. Reproduced with permission.
Dopamine: Dopamine, molecular structure, photograph. Hans & Cassidy. Courtesy of Gale Research.
Dopamine: Dopamine, enlarged pictures, photograph. Hans & Cassidy. Courtesy of Gale Research.
Doppler effect: Doppler effect, train inbetween two stations, illustration. Hans & Cassidy. Courtesy of Gale Research.
Doppler effect: Doppler effect, illstration. Hans & Cassidy. Courtesy of Gale Research.
Dormouse: Dormouse holding branch, photograph. © Jane Burton, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Down's syndrome: Down's syndrom, children, photograph. © Susan Woog Wagner, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Dragonfly: Dragonfly, photograph. © Jeanne White, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Draper, Charles Stark: Draper, Charles Stark, portrait. The Library of Congress.
Driftnet: Driftnet, photograph. © Rowlands, Greenpeace. Reproduced with permission.
Drought: Drought effect, Botswana, photograph. © Tom Nebbia/Stock Market. Reproduced with permission.
du Vigneaud, Vincent: du Vigneaud, Vincent, portrait. The Library of Congress.
Dubois, Eugene: Dubois, Eugene, photograph. The Library of Congress.
Ducks: Ducks, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Ducks: Ducks, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Dugong: Dugong, lagoon, photograph. © Fred McConnaughey, Photo Researchers, Inc. Reproduced with permission
Dulbecco, Renato: Dulbecco, Renato, portrait. The Library of Congress.
Dune: Dermid, Jack. Sand dunes, moving dunes, photograph. © Jack Dermid, National Audubon Society Collection/Photo Researchers, Inc.Reproduced with permission.
Dust devils: Dust devil, photograph. JLM Visuals. Reproduced with permission.
Dust storm: Dust storm (during the Great Depression), photograph. The Library of Congress.
Dyes and pigments: Textiles, fibric dye, photograph. © Randy Duchaine/Stock Market. Reproduced with permission.
Dyslexia: Right hand writing dyslexically, photograph. © Will & Deni McIntyre/Science Source, National Audubon Society Collection/ Photo Researchers, Inc. Reproduced with permission.
Dysplasia: Micrograph of cervical smear, photograph. © Jonathan Ashton/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Eagles: Eagles, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Ear: Ear, diagram of anatomy, photograph. Hans & Cassidy. Courtesy of Gale Research.
Earth: Space view of earth, photograph. U. S. National Aeronautics and Space Administration (NASA).
Earth: Earth rising over moon, photograph. U. S. National Aeronautics and Space Administration (NASA).
Earth Science: Geosphere project, view of North America, photograph. © Tom Van Sant/Stock Market. Reproduced with permission.
Earth's interior: Earth’s interior, illustration. Robert L. Wolke. Reproduced with permission.
Earth's interior: Earth's interior, diagram, photograph. Hans & Cassidy. Courtesy of Gale Research.
Earth's magnetic Field: Earth's magnetic field, photograph. © NASA /Phototake NYC Reproduced with permission.
Earthquake: Alaska, Earthquake, photograph. JLM Visuals. Reproduced with permission.
Earthquake: Earthquake in Chatsworth, January 17, 1994. Robert A. Eplett/OES/Governor’s Office of Emergency Services.
Earthquake: Satellite view of earthquake, photograph. © Massonnet ET AL, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Earthquake measurement scale: Earthquake measurement scale, photograph. (c) C. D. Miller/U. S. Geological Survey Photographic Library Denver, CO. Reproduced with permission. Eastern European Pollution: Eastern European Pollution. © K. Martensen, Greenpeace. Reproduced with permission.
Eccles, John C.: Eccles, John C., portrait. The Library of Congress.
Eclipse: Solar eclipse, photograph. © Francois Gohier/Science Source, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Ecojustice: Ecojustice, photograph. © Zachary Singer, Greenpeace. Reproduced with permission.
Ecological disturbance: Bare trees in open field, photograph. JLM Visuals. Reproduced with permission.
Ecological economics: Ecological economics. © Sam Kittner, Greenpeace. Reproduced with permission.
Ecological integrity: Ecological integrity, photograph. Lee Klinger, National Center for Atmospheric Research/University Corporation for Atmospheric Research/National Science Foundation 1225. Reproduced with permission.
Ecological Monitoring: Ecological monitoring, photograph. © R. L. Elderkin, Jr., U. S. Geological Survey.
Ecological pyramids: Ecological pyramids, line drawing. Hans & Cassidy. Courtesy of Gale Research.
Ecologists, Biologists: Ehrlich, Paul, (cigar in hand), photograph. The Library of Congress.
Ecology: Ecology, photograph. © Robert F. Bailey, U. S. Forest Service.
Ecosystem: Ecosystem, underwater, illustration. Hans & Cassidy. Courtesy of Gale Research.
Ecosystem: Ecosystem, illustration. Hans & Cassidy. Courtesy of Gale Research.
Ecotone: Boundy between Pikes Peak and Ramparts Range, photograph. © W. B. Hamilton. U. S. Geological Survey Photographic Library Denver, Colorado.
Edelman, Gerald: Edelman, Gerald, portrait. The Library of Congress.
Edema: Lymphoedema in arm, elderly woman, photograph. © Dr. P. Marazzi, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Edison, Thomas Alva: Edison, Thomas Alva, portrait. The Library of Congress.
Eel: Eel swimming, photograph. © James T. Spencer, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

El nino and la nina: El nino and la nina, photograph. National Center for Atmospheric Research/University Corporation for Atmospheric Research/National Science Foundation 756. Reproduced with permission.
Eland: Bull eland, photograph. © Suen-O Linoblad,National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Elapid snakes: Cobra, photograph. © Tom McHugh, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Electric Circuit: Electric circuit, man working on electric control panals, photograph. © Rick Altman/Stock Market. Reproduced with permission.
Electric Current: Electric current between two objects, photograph. © Phil Jude, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Electric motor: Direct current motor, photograph. © Bruce Iverson/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Electrical power supply: Interior image, electrical power plant, photograph. JLM Visuals. Reproduced with permission.
Electricity: Ceramic insulators, photograph. Robert Essel/Bikderberg/Stock Market. Reproduced with permissions.
Electrocardiogram: Electrocardiogram, Doctor with patient, photograph. © Mug Shots/Stock Market. Reproduced with permission.
Electrocardiogram (ECG): Electrocardiogram, diagrams, photograph. Hans & Cassidy. Courtesy of Gale Research.
Electrocardiogram (ECG): Electrocardiogram, electrode placement points, photograph. Hans & Cassidy. Courtesy of Gale Research.
Electrocardiogram (ECG): Electrocardiogram, graph, deflections and intervals, photograph. Hans & Cassidy. Courtesy of Gale Research.

Electrocardiogram (ECG): Electrocardiogram, rhythm charts, photograph. Hans & Cassidy. Courtesy of Gale Research.
Electrocephalogram (EEG): Woman undergoing EEG, photograph. © Catherine Pouedras/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced by permission.
Electrolysis: Electolysis, photograph. Robert L. Wolke. Reproduced by permission.
Electrolyte: Electolyte, photograph. Robert L. Wolke. Reproduced by permission.
Electromagnetic Field: Electromagnetic field, electrons, photograph. © John Howard, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Electromagnetic induction: Electromagnetic induction, illustration, photograph. Hans & Cassidy. Courtesy of Gale Research.
Electromagnetic induction: Electromagnetic induction, chats, photograph. Hans & Cassidy. Courtesy of Gale Research.
Electromagnetic induction: Electromagnetic induction, chart, illustration. Hans & Cassidy. Courtesy of Gale Research.
Electromagnetic induction: Electromagnetic induction, light bulb, photograph. Hans & Cassidy. Courtesy of Gale Research.
Electromagnetic spectrum: Electromagnetic spectrum, illustration. Robert L. Wolke. Reproduced with permission.
Electron: Electron, illustration. Hans & Cassidy. Courtesy of Gale Research.
Electron Microscope: Electron microscope, SEM screens, photograph. © Philippe Plailly/Eurelious/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Electronics: Computer chip board, photograph. © Peter Vadnai/Stock Market. Reproduced with permission.
Electrophoresis: Electrophoresis, DNS, photograph. Hans & Cassidy. Courtesy of Gale Research.
Electrophoresis: Electrophoresis, moving boundary electrophoresis, illustration. Hans & Cassidy. Courtesy of Gale Research.
Electrophoresis: Electrophoresis, SDS-Page Gel, photograph. Hans & Cassidy. Courtesy of Gale Research.
Electrostatic device: Van de Graff generator, photograph. © Adam Hart-Davis/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Element| transuranium: Element transuranium, illustration. Hans & Cassidy. Courtesy of Gale Research.
Element, transuranium: Element transuranium, illustration. Hans & Cassidy. Courtesy of Gale Research.
Elephant shrew: Elephant shrew, photograph. © Tom McHugh, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Elephant snout fish: Elephant lip-fish, photograph. © Jean-Michel, National Audubon Society Collection/ Photo Researchers, Inc. Reproduced with permission
Elephantiasis: Elephantiasis in leg, photograph. C. James Webb/Phototake NYC. Reproduced with permission.
Elephants: Elephant, Asian, photograph. © Ben Simon/Stock Market. Reproduced with permissions.
Elephants: Elephants, photograph. Michael Burgess/Bikderberg/Stock Market. Reproduced with permissions.
Elevator: Architecture, skyward interior of hotel, photograph. © Kacs Maciag/Stock Market. Reproduced with permission.
Elm: Elm, photograph. James Lee Sikkema. Reproduced by permission.
Embroyo and Embroyonic: Human fetus, five to six weeks, photograph. © Petit Fromat/Nestle, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Embryology: Embryology, turnips, photograph. © Dr. Jeremy Burgess, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Emission: Pollution, Nickel smelter, photograph. © J. Polleross/Stock Market. Reproduced with permission.
Endangered Species: Golden frog, photograph. JLM Visuals. Reproduced with permission.
Endemic: Endemic, photograph. © Chris Childs, Greenpeace. Reproduced with permission.
Endemic species: Endemic species, photograph. © Luther C. Goldman, National Park Service.
Enders, John F.: Enders, John F., portrait. The Library of Congress.
Endoscopy: Larynx endoscopy, photograph. © National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Endothermic: (c) U.S. Fish & Wildlife Service.
ENER 1957: Nuclear reactors, portrait. The Library of Congress.
Energy: Waterfall, photograph. JLM Visuals. Reproduced with permission.
Energy and the environment: Energy and the environment, photograph. U. S. Department of Energy, Washington DC.
Energy Paths: Energy paths, photograph. © James Perez, Greenpeace. Reproduced with permission.
Energy paths: Energy paths, photographs. U. S. Department of Energy, Washington DC.
Engineering: Computer aided work station, man, photograph. © David Parker/Science Photo Library, The National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Engineering: Engineering, men with blueprints, photograph. © Vadnai/Stock Market. Reproduced with permission.
English, Naturalists: Darwin, Charles, photograph. The Library of Congress.
Engraving/etching: Nowitz, Richard. Laser etching, man with machinery, photograph. © Richard Nowitz/Phototake NYC. Reproduced with permission.

Enterobacteria: Enterobacteria, photograph. © CNRI/Science Photo Library, National Audubon Society Collection/ Photo Researchers, Inc. Reproduced with permission.
Environmental ethics: Environmental ethics. © Keith Grove. Courtesy of U. S. Forest Service.
Environmental Science: Environmental science, photograph. © Midgley, Greenpeace. Reproduced with permission.
Environmentalism: Environmentalism, photograph. © Jay Townsend, Greenpeace. Reproduced with permission.
Enzyme: Pepsinogen, pepsin, photograph. © Ken Eward/Science Source/,National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Enzyme: Enzyme, L-Alanine, photograph. Hans & Cassidy. Courtesy of Gale Research.
Enzyme: Enzyme, tripeptide, illustration. Hans & Cassidy. Courtesy of Gale Research.
Enzyme: Enzyme, lock-and-key model of interaction, illustration. Hans & Cassidy. Courtesy of Gale Research.
Enzyme: Enzyme: reaction vs. energy, illustration. Hans & Cassidy. Courtesy of Gale Research.
Enzyme: Enzyme feedback mechanism, illustration. Hans & Cassidy. Courtesy of Gale Research.
Enzyme: Enzyme, phosphate group transfer, photograph. Hans & Cassidy. Courtesy of Gale Research.
Ericsson, John: Ericsson, John, portrait. The Library of Congress.
Erlanger, Joseph: Erlanger, Joseph, portrait. The Library of Congress.
Erosion: Soil erosion, Kenya, photograph. © Mark Boulton, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Ester: Ester, illustration. Robert L. Wolke. Reproduced with permission.
Ethanol: Ethanol, photograph. U. S. Department of Energy, Washington DC.
Ether: Crown Ether, photograph. © Ken Eward/BioGrafx/Science Source, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Ethnologists: Goodall, Jane, photograph. The Library of Congress.
Euclid: Euclid, photograph of sketch. The Library of Congress.
Eulor, Leonhard: Eulor, Leonhard, portrait. The Library of Congress.
Europe: Lone esate, European valley, photograph. JLM Visuals. Reproduced with permission.
Europe: Satellite view of North and South America, photograph. © 90 Photri/Stock Market. Reproduced with permission.
Europe: Europe, illustration. Hans & Cassidy. Courtesy of Gale Research.
Europe: Europe, map, photograph. Hans & Cassidy. Courtesy of Gale Research.
Eutrophication: Eutrophic Lake, photograph. © Joyce Photographics, National Auduobon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Eutrophication: Eutrophic lake, factory, photograph. Hans & Cassidy. Courtesy of Gale Research.
Evapotranspiration: Evapotranspiration, photograph. National Center for Atmospheric Research/University Corporation for Atmospheric Research/National Science Foundation 1016. Reproduced with permission.
Evapotranspiration: Evapotranspiration, illustration. Hans & Cassidy. Courtesy of Gale Research.
Evapotranspiration: Evapotranspiration, forest, chaparral, illustration. Hans & Cassidy. Courtesy of Gale Research.
Everglades: Everglades, photograph. © Richard Frear , National Park Service Photo. Reproduced with permission.
Evolution adaptation: Evolution adaption, giraffe, photograph. © Stan Osolinski/Stock Market. Reproduced with permission.
Exotic species: Exotic species, photograph. © U.S. Fish & Wildlife Service.
Explosives: Nuclear explosion, photograph. © Photri/Stock Market. Reproduced with permission.
Exxon Valdez oil spill: Exxon Valdez oil spill, photograph. © Merjenburgh, Greenpeace. Reproduced with permission.
Eye: Eye, illustration. Hans & Cassidy. Courtesy of Gale Research.
Falcon: Immature peregrine flying, photograph. © Mark Wilson, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Falcon: Falcon, photograph. Robert J. Huffman/Field Mark Publications. Reproduced with permission.
False teeth: False teeth, photograph. The Library of Congress.
Forces, four fundamental: Gravity wave research, photograph. © Tommaso Guicciardini/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Farming, mass production: Farming, mass production , corn, photograph. © Jeff Greenberg, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Fatty acid: Fatty acid, illustration. Robert L. Wolke. Reproduced with permission.
Fault: San Andreas Fault, photograph. JLM Visuals. Reproduced with permission.
Fault: Faults, illustration. Hans & Cassidy. Courtesy of Gale Research.
Fault: Faults, seventy degree angle, photograph. Hans & Cassidy. Courtesy of Gale Research.
Fault: Faults, illustration. Hans & Cassidy. Courtesy of Gale Research.
Fault: Faults, three illustrations of earth, photograph. Hans & Cassidy. Courtesy of Gale Research.
Ferns: Ferns, photograph. Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Ferns: Fern leaves, photograph. JLM Visuals. Reproduced with permission.
Ferrel, William: Ferrel, William, portrait. The Library of Congress.
Ferret: Ferret, photograph. JLM Visuals. Reproduced with permission.
Fertilization: Fertilization of hamster egg, photograph. © David M. Phillips/The Population Council/Science Source, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Fertilizers: Fertilizers, photograph. © Thomas Del Brase, Stock Market. Reproduced with permission.
Fertilizers: Fertilizers, photograph. National Center for Atmospheric Research/University Corporation for Atmospheric Research/National Science Foundation 312. Reproduced with permission.
Feynman, Richard P.: Feynman, Richard P., photograph. The Library of Congress.
Fiber optics: Fiber optics bundle, photograph. © Erich Schrempp, The National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Fiber optics: Fiber optics, diagram, illustration. Hans & Cassidy. Courtesy of Gale Research.
Fiber optics: Fiber optics, flow chart, input, output signal, photograph. Hans & Cassidy. Courtesy of Gale Research.
Fiber optics: Fiber optics, incidence, reflection, illustration. Hans & Cassidy. Courtesy of Gale Research.
Fiber optics: Fiber optics, graph angle of incidence, reflection, illustration. Hans & Cassidy. Courtesy of Gale Research.
Fiber optics: Fiber optics, critical angle, angle of refrection, photograph. Hans & Cassidy. Courtesy of Gale Research.
Fiber optics: Fiber optics, graph, photograph. Hans & Cassidy. Courtesy of Gale Research.
Fiber optics: Fiber optics, graph, photograph. Hans & Cassidy. Courtesy of Gale Research.
Fiber optics: Fiber optics, step-index multimode, photograph. Hans & Cassidy. Courtesy of Gale Research.
Fiber optics: Fiber optics, graded index multimode, photograph. Hans & Cassidy. Courtesy of Gale Research.
Fiber optics: Fiber optics, single-mode step index, photograph. Hans & Cassidy. Courtesy of Gale Research.
Fibiger, Johannes: Fibiger, Johannes, portrait. The Library of Congress.
Figurative numbers: Figurative numbers, triangles, photograph. Hans & Cassidy. Courtesy of Gale Research.
Figurative numbers: Figurative numbers, illustration. Hans & Cassidy. Courtesy of Gale Research.
Figurative numbers: Figurative numbers, pentagon, photograph. Hans & Cassidy. Courtesy of Gale Research.
Figurative numbers: Figurative numbers, dots, diagnol line, photograph. Hans & Cassidy. Courtesy of Gale Research.
Figurative numbers: Figurative numbers, pentagon, illustration. Hans & Cassidy. Courtesy of Gale Research.
Figurative numbers: Figurative numbers, square, diagnol line, photograph. Hans & Cassidy. Courtesy of Gale Research.
Figurative numbers: Dotted pentagon, three diagnol lines going through, illustration. Hans & Cassidy. Courtesy of Gale Research.
Figurative numbers: Figurative numbers, three dotted rectangles, photograph. Hans & Cassidy. Courtesy of Gale Research.
Finches: Ground finch, photograph. © Tim Davis, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Finches: Finches, photograph. Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Firearms: Firearms, diagram of handgun, photograph. Hans & Cassidy. Courtesy of Gale Research.
Firs: Firs, photograph. James Lee Sikkema. Reproduced with permission.
Fischer, Emil: Fischer, Emil, portrait. The Library of Congress.
Fischer, Hans: Fisher, Hans, portrait. The Library of Congress.
Fish kills: Fish kills, photograph. © U.S. Fish & Wildlife Service.
Fitch, John: Fitch, John, portrait. The Library of Congress.
Flagella: Cilia, flagella, photograph. © Fawcett/Phillips, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Flamingoes: Flamingos, photograph. © Nigel Dennis, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Flatfish: Windowpane flounder, photograph. © Andrew J. Martinez, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Flatworms: Liver Fluke, photograph. JLM Visuals. Reproduced with permission.
Flax: Dandelions, photograph. JLM Visuals. Reproduced with permission.
Fleas: Flea, photograph. © Phillip A. Harrington/Stock Market. Reproduced with permission.
Flies: Flies, life stages, diagram, illustration. Hans & Cassidy. Courtesy of Gale Research.
Flightless Birds: Bird, ostrich, photograph. © Michele Burgess/Stock Market. Reproduced with permissions.
Flooding: Arizona, Salt River, AZ., photograph. JLM Visuals. Reproduced with permission.
Florey, Howard Walter: Florey, Howard Walter, photograph. The Library of Congress.
Florida Panther: Panther sitting in tree, photograph. © David Lawrence/Stock Market. Reproduced with permission.
Flourescence: Flourescence, mineral splt frame, photograph. JLM Visuals. Reproduced with permission.
Flourescence: Flourescence, non-radiative energy loss, illustration. Hans & Cassidy. Courtesy of Gale Research.
Fluid dynamics: Fluid dynamics, plane design, photograph. U. S. National Aeronautics and Space Administration (NASA).
Fluid mechanics: Fluid mechanics, diagram, illustration. Hans & Cassidy. Courtesy of Gale Research.
Fluoridation: Flouridation, water, photograph. © Tom Carroll/Phototake NYC Reproduced with permission.
Fold: Large fold, photograph. JLM Visuals. Reproduced with permission.
Food irradiation: Food irradiation, chart, photograph. Hans & Cassidy. Courtesy of Gale Research.
Force: Center of gravity, drill into center of wood, photograph. © Charles D. Winters, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Forensic science: Fingerprints, forensics, photograph. © Account Phototake/Phototake NYC. Reproduced with permission.
Forest: Forest, Deciduous trees, photograph. © Zefa Germany/Stock Market. Reproduced with permission.
Forest and Rangeland Planning Act: Forest and Rangeland Planning Act. © Jill Bauermeister. Courtesy of U. S. Forest Service.
Forest decline: Tropical rainforest, tractor-trailer truck, photograph. © Fletcher W. K. , National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Forestry: Forestry, woman aging a tree, photograph. © Tom Bean/Stock Market. Reproduced with permission.
Forestry: Forestry. © Yuen-Gi Yee. Courtesy of U. S. Forest Service.
Forests: Rainforest, photograph. © Zefa Germany, Stock Market. Reproduced by permission
Formula| structural: Formula structural, ethanol, dimethyl ether, illustration. Hans & Cassidy. Courtesy of Gale Research.
Fossa: Fossa, photograph. © National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Fossil: Insect minerals, Amber, photograph. JLM Visuals. Reproduced with permission.
Fossil: Fossil, photograph. © Neasaphus Rowalewkii. Reproduced with permission.
Fossil and Fossilization: Fossil and Fossilization, photograph. Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Fossil fuels: Scientists working on lasor device, photograph. © US Department of Education, The National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Fossils and Fossilization: "Lucy's" bones, skeleton, photograph. © Tom McHugh/Science Source, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Fourier, Jean-Baptiste Joseph: Fourier, Jean-Baptiste Joseph, portrait. The Library of Congress.
Fowler, William A.: Fowler, William A., portrait. The Library of Congress.
Fractal: Fratal, three lines, photograph. Hans & Cassidy. Courtesy of Gale Research.
Fractals: Mathmeticians and scientists, photograph. © Geoffrey Clifford/Stock Market. Reproduced with permissions.
Francis, Joseph: Francis, Joseph, portrait. The Library of Congress.
Frank, Il'ya: Frank, Il'ya, portrait. The Library of Congress.
Frankland, Edward: Frankland, Edward, portrait. The Library of Congress.
Fraunhofer, Joseph von: Fraunhofer, Joseph von, portrait. The Library of Congress.
Freeway: Southern California freeway system, photograph. © Tom Carroll/Phototake NYC. Reproduced with permission.
Freshwater: Flowing water, rock mountain, photograph. JLM Visuals. Reproduced with permission.
Frigate Bird: Bird, Frigate, photograph. © Ormond Gigli/Stock Market. Reproduced with permissions.
Frog: Red-eyed treefrog, photograph. JLM Visuals. Reproduced with permission.
Frogs: Frogs, photograph. Robert J. Huffman/Field Mark Publications. Reproduced with permissions.
Frostbite: Human hand, frostbite, photograph. © SIU, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Fuller, Buckminster: Fuller, Buckminster, portrait. The Library of Congress.
Function: Graphic of mathematical function, photograph. © Alfred Pasteka/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Fungi: Fungi, photograph. Robert J. Huffman/Field Mark Publications. Reproduced with permissions.
Future generations: Future generations, photograph. © Morgan, Greenpeace. Reproduced with permissions.
Galapagos flightless cormorant: Flightless cormorant, drying wings, photograph. © Irene Vandermolen, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Galapagos Hawk: Galapagos Hawk, photograph. © Carolina Biological Supply/Phototake NYC Reproduced with permission.
Galapagos tortoise: Galapagos tortoise, photograph. © U.S. Fish & Wildlife Service.
Galaxy: Andromeda galaxy, photograph. © Tony Ward/Science Photo Library. Reproduced with permission.
Galaxy: Andromeda galaxy, photograph. California Institute of Technology and Carnegie Institution of Washington/U. S. National Aeronautics and Space Administration (NASA).
Galen: Galen, photograph of bust. The Library of Congress.

Gallium: Gallium melting in hand, photograph. © Russ Lappa/Science Source, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Galton, Francis: Galton, Francis, portrait. The Library of Congress.
Gamow, George: Gamow, George, photograph. The Library of Congress.
Gangrene: Gangrene in toes, diabetic patient, photograph. © Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Garbage: Garbage, photograph. © Robert Visser, Greenpeace. Reproduced with permission.
Garpike: Garpike, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Gases: Gases, illustration. Robert L. Wolke. Reproduced with permission.
Gases: Gases, illustration. Robert L. Wolke. Reproduced with permission.
Gases, properties of: Gases, properties, illustration. Robert L. Wolke. Reproduced with permission.
Gases, properties of: Gases, properties, illustration. Robert L. Wolke. Reproduced with permission.
Gases, properties of: Two bottles, clear liquid, photograph. © Charles D. Winters, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Gasser, Herbert Spencer: Gasser, Herbert Spencer, portrait. The Library of Congress.
Gatling, Richard Gordon: Gatling, Richard Gordon, portrait. The Library of Congress.
Gauss, Carl Friedrich: Gauss, Carl Friedrich, portrait. The Library of Congress.
Gay-Lussac, Joseph: Gay-Lussac, Joseph, photograph. The Library of Congress.
Gazelle: Gazelle, Kenya, photograph. © James Allen/Stock Market. Reproduced with permission.
Gecko: Gecko, photograph. © Streinhart Aquarium, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Geese: Geese, photograph. Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Gell-Man, Murray: Gell-Man, Murray, portrait. The Library of Congress.
Gene: Genes, false colored image, photograph. © Howard Sochurek/Stock Market. Reproduced with permission.
Gene Therapy: DNA microinjection, photograph. © Philippe Plailly, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Generator: Hydroelectric power plant generator, photograph. © Jon Reis/Stock Market. Reproduced with permission.
Genet: Genet, photograph. © Mary M. Thacher, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Genetic disorders: Down's syndrome, genetic disorders. © Account Phototake/Phototake NYC. Reproduced with permission.
Genetic engineering: Genetic engineering, twp sheep, photograph. © Philippe Plailly, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Genetics: Genetics, twins, photograph. © Gerald Davis/Phototake NYC Reproduced with permission.
Geocentric theory: Geocentric theory, planets, photograph. Hans & Cassidy. Courtesy of Gale Research.
Geodesic Dome: Geodesic radar dome, photograph. © John Heseltine, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Geologic time: Geologic time, time-line, photograph. Hans & Cassidy. Courtesy of Gale Research.
Geology: Geology, photograph. U. S. Geological Survey Photographic Library Denver, CO.
Geometry: Computer diagram, geometry, photograph. © Richard Duncan,National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Geometry: Geometry, angles, photograph. Hans & Cassidy. Courtesy of Gale Research.
Geometry: Geometry, triangle, photograph. Hans & Cassidy. Courtesy of Gale Research.
Geometry: Geometry, triangle, photograph. Hans & Cassidy. Courtesy of Gale Research.
Geometry: Geometry, circle, triangle, photograph. Hans & Cassidy. Courtesy of Gale Research.
Geometry: Geometry, circle, cone, illustration. Hans & Cassidy. Courtesy of Gale Research.
Geothermal energy: Steam wells, New Zealand, photograph. JLM Visuals. Reproduced with permission.
Gerbil: Gerbil, photograph. JLM Visuals. Reproduced with permission.
Gesnarias: Gesnarias, photograph. James Lee Sikkema. Reproduced by permission.
Giauque, William F.: Giauque, William F., portrait. The Library of Congress.
Gibbons: Gibbon, photograph. © Tom McHugh, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Gibbons and Siamangs: Gibbon sitting on rocks, photograph. © Michele Burgess/Stock Market. Reproduced with permission.
Gibbs, Josiah: Gibbs, Josiah, photograph of painting. The Library of Congress.
Gila Monster: Gila Monster, photograph. © Allan D. Cruickshank, National Audubon Society Collections/Photo Researchers, Inc. Reproduced with permission.
Gilbert, William: Gilbert, William, photograph of painting. The Library of Congress.
Ginger: Ginger plant, photograph. JLM Visuals. Reproduced with permission.
Ginkgo: Ginkgo tree, photograph. JLM Visuals. Reproduced with permission.
Ginseng: American ginseg, photograph. JLM Visuals. Reproduced with permission.
Giraffe: Giraffes, photograph. © Clem Haagner, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Glacier: Muir Glacier, Glacier Bay, photograph. JLM Visuals. Reproduced with permission.
Glacier: Hubbard glacier, photograph. © Mark Newman/Phototake NYC. Reproduced with permission.
Glaser, Donald: Glaser, Donald, portrait. The Library of Congress.
Glass: Glass-blowing, photograph. © J. Kubec/Stock Market. Reproduced with permission.
Glen Canyon Dam: Glen Canyon Dam, Az., photograph. © Kunio Owaki/Stock Market. Reproduced with permission.
Global Climate: Map of global cloud, photograph. © NASA Goddard Institute For Space Studies/ Mark Marten, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Global climate: National Center for Atmospheric Research/University Corporation for Atmospheric Research/National Science Foundation 728. Reproduced with permission.
Glycol: Glycol, equation Ethylene glycol, terephthalic acid, polyethylene, photograph. Hans & Cassidy. Courtesy of Gale Research.
Glycol: Glycol, four molecular structures, illustration. Hans & Cassidy. Courtesy of Gale Research.
Glycol: Molecular structure of an alkene and glycol, photograph. Hans & Cassidy. Courtesy of Gale Research.
Glycol: Glycol, equation Ethylene oxide, glycol, photograph. Hans & Cassidy. Courtesy of Gale Research.
Goats: Goats, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Goats: Markhor, jagged rocks, photograph. © A. W. Ambler, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Gobies: Mudskipper, Indo-pacific, photograph. JLM Visuals. Reproduced with permission.
Goddard, Robert H.: Goddard, Robert H., portrait. The Library of Congress.
Gold: Gold, quartz, photograph. JLM Visuals. Reproduced with permission.
Golgi, Camillo: Golgi, Camillo, portrait. The Library of Congress.
Gopher: Pocket gopher, photograph. © Verna R. Johnston, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Gorilla: Gorillas, adult male, juvenile, photograph. © Tom McHugh, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Gourd family: Gourd family, photograph. Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Gourd family: Squash, photograph. JLM Visuals. Reproduced with permission.
Gourd Family: Cucumber, photograph. JLM Visuals. Reproduced with permission.
Graham, Thomas: Graham, Thomas, portrait. The Library of Congress.
Grapes: Grapes, photograph. James Lee Sikkema. Reproduced by permission.
Grasses: Grasses, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Grasses: Grasses, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Grasses: Grass, photograph. JLM Visuals. Reproduced with permission,
Grasshopper: Grasshopper, photograph. JLM Visuals. Reproduced with permission.
Grasslands: Grasslands, prairie, photograph. © Bill Bachman, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Gravitational Lens: Huchra's cross, photograph. © Space Telescope Science Institute/NASA/ Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Gravity and gravitation: Six astronauts, sitting in circle, photograph. U. S. National Aeronautics and Space Administration (NASA).
Gravity and gravitation, Astronauts: Astronauts (float in cargo bay), photograph. U. S. National Aeronautics and Space Administration.
Gray, Elisha: Gray, Elisha, portrait. The Library of Congress.
Great Bustard: Great Bustard, photograph. © Toni Angermayer , National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Great Indian Rhinoceros: Great Indian Rhinoceros, photograph. © Mark N. Boulton, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Great Lakes: Great lakes, photograph. Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Grebes: Western grebes, South Dakota, photograph. © Jen and Des Bartlett, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Greenhouse effect: Greenhouse effect, photograph. © Thomas Bettge, National Center for Atmospheric Research/University Corporation for Atmospheric Research/National Science Foundation 555. Reproduced with permission.
Greenhouse effect: Greenhouse effect, photograph. National Center for Atmospheric Research/University Corporation for Atmospheric Research/National Science Foundation 556. Reproduced with permission.
Greenhouse effect: Greenhouse effect, two illustrations, photograph. Hans & Cassidy. Courtesy of Gale Research.
Grizzly bear: Grizzly bear, photograph. National Park Service, Harpers Ferry Center.
Ground water: Seeping aquifer, photograph. JLM Visuals. Reproduced with permission.
Groundhog: Groundhog, photograph. © Leonard Lee Rue III, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Groundwater Pollution: Groundwater pollution, photograph. © Sandra Marquardt, Greenpeace. Reproduced with permission.
Grouse: Canada, Quebec, Willow, ptarmigan, photograph. JLM Visuals. Reproduced with permission.
Guericke, Otto von: Guericke, Otto von, portrait. The Library of Congress.
Guinea fowl: Guinea fowl, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Gulls: Gulls, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Gynecology: Gynecology, speculum, photograph. © Simon Fraser, Custom Medical Stock Photo, Inc. Reproduced by permission.
Gypsy Moth: Gypsy moth, tree branch, photograph. JLM Visuals. Reproduced with permission.
Gyroscope: Gyroscope, photograph. © Al Francekevich/ Stock Market. Reproduced with permission.
Haeckel, Ernst: Haeckel, Ernst, portrait. The Library of Congress.
Hafnium: Hafnium, photograph. © Russ Lappa/Science Source/,National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Hahn, Otto: Hahn, Otto, photograph. The Library of Congress.
Haitian Solenodon: Haitian Solenodon, photograph. © N. Smythe, National Audubon Society Collection/ Photo Researchers, Inc. Reproduced with permission.
Hales, Stephen: Hales, Stephen, photograph of engraving. The Library of Congress.
Haller, Albrecht von: Haller, Albrecht von, portrait. The Library of Congress.
Halley, Edmond: Halley, Edmond, portrait. The Library of Congress.
Halley's Comet: Halley’s Comet, photograph. © Science Photo Library, National Audubon Society Collection/ Photo Researchers, Inc. Reproduced with permission.
Halsted, William Stewart: Halsted, William Stewart, portrait. The Library of Congress.
Hamilton, William: Hamilton, William, portrait. The Library of Congress.
Hamster: Goldhamster, stick, photograph. © Toni Angermayer, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Hancock, Thomas: Hancock, Thomas, portrait. The Library of Congress.
Harden, Arthur: Harden, Arthur, photograph. The Library of Congress.
Harrison, John: Harrison, John, portrait. The Library of Congress.
Hartebeestes: Cooke's hartebeest, photograph. JLM Visuals. Reproduced with permission.
Harvey, William: Harvey, William, drawing. The Library of Congress.
Hawaiian islands: M. Woodbridge Williams, National Park Service.
Hawiian Monk Seal: Hawiian Monkey Seal, photograph. © Karl W. Kenyon, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Hawks: Hawks, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Hawks: Hawks, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Haworth, Walter: Haworth, Walter, portrait. The Library of Congress.
Hazardous waste: Hazardous waste site, photograph. © Alexander Lowry, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Hearing: Hearing, diagram of human system, photograph. Hans & Cassidy. Courtesy of Gale Research.
Hearing disorders: Hearing test, baby, photograph. © James King-Holmes/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Heart: Heart valve, photograph. © Proff. P. Motta/G. MacchiarelliUniversity "La Sapienza," Rome/Science Photo Library, National Audubon Society Collection/ Photo Researchers, Inc. Reproduced with permission.
Heart: Heart, large diagram, photograph. Hans & Cassidy. Courtesy of Gale Research.
Heart: Heart, illustration. Hans & Cassidy. Courtesy of Gale Research.
Heart diseases: Coronary thrombosis, heart diseases, photograph. © Martin Rotker/Phototake NYC. Reproduced with permission.
Heart diseases: Heart disease, bar graph, countries, photograph. Hans & Cassidy. Courtesy of Gale Research.
Heat transfer: Heat transfer, water and copper, photograph. © Charles D. Winters, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Heath family: Heath family, photograph. James Lee Sikkema. Reproduced with permission.
Heath family: Heath family, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Heath family: Bush, pink flowers, photograph. JLM Visuals. Reproduced with permission.
Hedgehogs: African hedghog, photograph. JLM Visuals. Reproduced with permission.
Heisenberg, Werner Karl: Heisenberg, Werner Karl, photograph of sketch. The Library of Congress.
Helicopter: Helicopter, line drawing. Hans & Cassidy. Courtesy of Gale Research.
Helicopter: Helicopter, diagram, photograph. Hans & Cassidy. Courtesy of Gale Research.
Heliocentric theory: Heliocentric theory, inferior conjunction, superior conjunction, photgraph. Hans & Cassidy. Courtesy of Gale Research.
Heliocentric theory: Heliocentric theory, earth's orbit, celestial sphere, photograph. Hans & Cassidy. Courtesy of Gale Research.
Heliocentric theory: Heliocentric theory, deterent of the sun, photograph. Hans & Cassidy. Courtesy of Gale Research.
Helmholtz, Hermann von: Helmholtz, Hermann von, photograph of engraving. The Library of Congress.
Hemp family: Green plant, hemp family, photograph. JLM Visuals. Reproduced by permission.
Hench, Philip Showalter: Hench, Philip Showalter, portrait. The Library of Congress.
Herbicides: Herbicides, killed corn, photograph. © Ken Wagner /Phototake NYC. Reproduced with permission.
Hernia: Epigastric hernis, adult male, photograph. © John Bavosi, National Audubon Society Collection/ Photo Researchers, Inc. Reproduced with permission.
Herons and Egrets: Herons and egrets, photograph. Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Herons and Egrets: Herons and egrets, photograph. Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Herrings: Alewives, photographs. JLM Visuals. Reproduced with permission.
Herschel, Caroline; Herschel, Caroline, portrait. The Library of Congress.
Herschel, John Frederick: Herschel, Caroline, portrait. The Library of Congress.
Herschel, William: Herschel, William, portrait. The Library of Congress.
Hershey, Alfred Day: Hershey, Alfred Day, portrait. The Library of Congress.
Hertz, Gustav: Hertz, Gustav, portrait. The Library of Congress.
Hertz, Heinrich: Hertz, Heinrich, portrait. The Library of Congress.
Hertzsprung-Russell diagram: Hertzsprung-russel, graph, luminosity, spectral class, photograph. Hans & Cassidy. Courtesy of Gale Research.

Hertzsprung-Russell diagram: Hertzsprung Russell diagram, temperature vs. L/L, illustration. Hans & Cassidy. Courtesy of Gale Research.
Hertzsprung-Russell diagram: Hertzprung Russell diagram, temperature vs. L/L, turn-off point, photograph. Hans & Cassidy. Courtesy of Gale Research.
Hess, Victor: Hess, Victor, portrait. The Library of Congress.
Hetch Hetchy Reservoir: Hetch Hetchy Reservoir, photograph. © F. E. Matthes, U. S. Geological Survey.
Hetch Hetchy Reservoir: Hetch Hetchy Reservoir, photograph. © F. E. Matthes, U. S. Geological Survey Photographic Library Denver, CO.

Hewlett, William: Hewlett, William portrait. The Library of Congress.
Heymans, Corneille Jean-Francois: Heymans, Corneille Jean-Francois, portrait. The Library of Congress.
Heyrovsky, Jaroslav: Heyrovsky, Jaroslav, portrait. The Library of Congress.
Hibernation: Chart of months, hibernation, illustration. Hans & Cassidy. Courtesy of Gale Research.
Hicks, Beatrice: Hicks, Beatrice, portrait. The Library of Congress.
Hill, Archibald V.: Hill, Archibald V., portrait. The Library of Congress.
Hinshelwood, Cyril N.: Hinshelwood, Cyril N., portrait. The Library of Congress.
Hippopotamus: Hippopotamus yawning, photograph. © Jeanne White, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Hodgkin, Alan Lloyd: Hodgkin, Alan Lloyd, portrait. The Library of Congress.
Hodgkin's disease: Dividing cell, Hodgkin's disease, photograph. © Dr. Andrejs Liepins, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Hoffmann, August Wilhelm von: Hoffmann, August Wilhelm von , portrait. The Library of Congress.
Hofstadter, Robert: Hofstadter, Robert, portrait. The Library of Congress.
Holland, John Philip: Holland, John Philip, portrait. The Library of Congress.
Hollerith, Herman: Hollerith, Herman, portrait. The Library of Congress.
Holley, Robert William: Holley, Robert William, photograph. The Library of Congress.
Hologram and Holgraphy: Hologram Venus de Milo statue, photograph. © Phillippe Plailly, National Audubon Society Collection/Photo Reseearchers, Inc. Reproduced with permission.
Homeostasis: Homeostasis, graph, time, blood pressure, photograph. Hans & Cassidy. Courtesy of Gale Research.
Hopkins, Frederick Gowland: Hopkins, Frederick Gowland, photograph of sketch. The Library of Congress.
Horizon: Horizon, photograph. Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Hornbills: Hornbills, photograph. JLM Visuals. Reproduced with permission.
Horse chestnut family: Plant, chesnut bush, photograph. JLM Visuals. Reproduced with permission.
Horses: Horses, photograph. © J. Gordon Miller. Reproduced with permission.
Horseshoe crabs: Horseshoe crabs, photograph. © Anne Heimann/Stock Market. Reproduced with permissions.
Horsetails: Horsetails, photograph. Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Horticulture: Herb garden design, photograph. © George Whiteley, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Hot spot: Hot spot, photograph. John P. Winter, National Park Service.
Houdry, Eugene: Houdry, Eugene, portrait. The Library of Congress.
Houssay, Bernardo: Houssay, Bernardo, portrait. The Library of Congress.
Huggins, Charles B.: Huggins, Charles B., portrait. The Library of Congress.
Huggins, William: Huggins, William, photograph. © Science Photo Library, National Audubon Society/Photo Researchers, Inc. Reproduced by permission.

Human-powered vehicles: Human-powered vehicles, photograph. The Library of Congress.
Humboldt, Alexander von: Humboldt, Alexander von, photograph of engraving. The Library of Congress.
Hummingbird: Hummingbird, photograph. © Zefa Germany/Stock Market. Reproduced by permission.
Humpback whale: Humpback whale, photograph. © U.S. Fish & Wildlife Service.
Hunter, John: Hunter, John, portrait. The Library of Congress.
Hurricane: Hurricane Diana, computer enhanced image, photograph. U. S. National Aeronautics and Space Administration (NASA).
Hutton, James: Hutton, James, photograph of painting. The Library of Congress.
Huxley, Andrew Fielding: Huxley, Andrew Fielding, portrait. The Library of Congress.
Huxley, Julian: Huxley, Julian, photograph. The Library of Congress.
Huygens, Christiaan: Huygens, Christiaan, photograph of painting. The Library of Congress.
Hydra: Brown Hydra, photograph. © Tom Branch/ Science Source, National Audubon Society Collection/ Photo Researchers, Inc. Reproduced with permission
Hydrocarbon: Hydrocarbon, illustration. Hans & Cassidy. Courtesy of Gale Research.
Hydrocarbon: Hydrocarbon, illustration. Hans & Cassidy. Courtesy of Gale Research.
Hydrocarbon: Hydrocarbon, carbon equation, illustration. Hans & Cassidy. Courtesy of Gale Research.
Hydrocarbon: Hydrocarbon, carbon equation, photograph. Hans & Cassidy. Courtesy of Gale Research.
Hydrocarbon: Hydrocarbon, carbon equation, illustration. Hans & Cassidy. Courtesy of Gale Research.
Hydrocarbon: Hydrocarbon, equation C, H, illustration. Hans & Cassidy. Courtesy of Gale Research.
Hydrocarbon: Hydrocarbon, equation, C, H, illustration. Hans & Cassidy. Courtesy of Gale Research.
Hydrocarbon: Hydrocarbon, benzene, photograph. Hans & Cassidy. Courtesy of Gale Research.
Hydrocarbon: Hydrocarbon, naphthalene, photograph. Hans & Cassidy. Courtesy of Gale Research.
Hydrocarbons: Hydrocarbons, illustration. Robert L. Wolke. Reproduced with permission.
Hydrocarbons: Hydrocarbons, illustration. Robert L. Wolke. Reproduced with permission.
Hydrocarbons: Hydrocarbons, illustration. Robert L. Wolke. Reproduced with permission.
Hydrochephalus: CNRI. CAT scan, hydrochephalus, photograph. © CNRI/Phototake NYC Reproduced with permission.
Hydrologic cycle: Hydrologic cycle, lake, forest, factory, photograph. Hans & Cassidy. Courtesy of Gale Research.
Hydrologic cycle: Hydrologic cycle, illustration. Hans & Cassidy. Courtesy of Gale Research.
Hydrology: Rain guage, photograph. JLM Visuals. Reproduced by permission.
Hydrology: Rain gauge, photograph. JLM Visuals. Reproduced with permission.
Hydrology: Rain guage, photograph. JLM Visuals. Reproduced by permission.
Hydrothermal Vent: Prince of Wales feather geysers, New Zealand, photograph. (c) Frederica Georgia, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Hydrothermal Vent: Morning Glory Pool, photograph. JLM Visuals. Reproduced with permission.
Hydrothermal vents: Hydrothermal vents, photograph. © Francis Leroy, Biocosmos/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Hydrothermal vents: Hydrothermal vents, photograph. © W. R. Normark/U. S. Geological Survey Photographic Library Denver, CO.
Hydrotherman vent: Morning Glory Pool, photograph. JLM Visuals. Reproduced with permission.
Hyena: Hyenas eating zebra, photograph. © Robert Caputo, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Hyman, Libbie Henrietta: Hyman, Libbie Henrietta, photograph. The Library of Congress.
Hyperbola: Hyperbola, plank, photograph. Hans & Cassidy. Courtesy of Gale Research.
Hyperbola: Hyperbola, photograph. Hans & Cassidy. Courtesy of Gale Research.
Hyperbola: Hyperbola, directrix, focus, photograph. Hans & Cassidy. Courtesy of Gale Research.
Hyperbola: Hyperbola, graph, photograph. Hans & Cassidy. Courtesy of Gale Research.
Hyperbola: Hyperbola, circle, photograph. Hans & Cassidy. Courtesy of Gale Research.
Hyperbola: Hyperbola, graph with shaded section, photograph. Hans & Cassidy. Courtesy of Gale Research.
Hyperbola: Hyperbola, graph, photograph. Hans & Cassidy. Courtesy of Gale Research.
Hyperbola: Hyperbola, graph, photograph. Hans & Cassidy. Courtesy of Gale Research.
Hyraxes: Rock hyrax, photograph. JLM Visuals. Reproduced with permission.
Ibises: Ibises, photograph. Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Ice age: Drumlin, Southern WS., photograph. JLM Visuals. Reproduced with permission.
Ice age refuges: Ice age refuges, photograph. R.A. Mittermeier, Conservation International. Reproduced with permission.
Icebergs: Icebergs, Greenland, photograph. © Tom Stewart/Stock Market. Reproduced with permission.
Igneous Rock: Pahoehoe Lava, Ha., photograph. JLM Visuals. Reproduced with permission.
Iguanas: Iguanas, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Immune system: Macrophage and lymphocyte, immune system. © Institut Pasteu/Phototake NYC. Reproduced with permission.
Immune system: Immune system, Flow chart, illustration. Hans & Cassidy. Courtesy of Gale Research.
Immune system: Immune system, T-cells, photograph. Hans & Cassidy. Courtesy of Gale Research.
Imperial Pheasant: Imperial pheasant, photograph. © Tom McHugh, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
In-vitro Fertilization: Egg fertilization, photograph. © Hank Morgan, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Incandescent light: Light bulb, photograph. © Yoav LevyPhototake NYC. Reproduced with permission.
Indium: Indium, photograph. © Russ Lappa/Science Source, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Industrial minerals: Matrix of diamond, photograph. U. S. National Aeronautics and Space Administration (NASA).
Industrialists: Slater, Samuel (head and shoulders), engraving. The Library of Congress.
Inequality: Inequality, line graph, photograph. Hans & Cassidy. Courtesy of Gale Research.
Inequality: Inequality, graph, left half shaded, illustration. Hans & Cassidy. Courtesy of Gale Research.
Infared Astronomy: United Kingdom Infrered Telescope, photograph. © Royal Observatory, Edinburgh/ Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Infection: Infection, sore throat. © Howard Sochurek/Stock Market. Reproduced with permission.
Influenza: Influenza virus, photograph. © CNRI/ Science Photo Library, Nationa Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Ingen-Housz, Jan: Ingen-Housz, Jan, portrait. The Library of Congress.
Innoculation: Innoculation, photograph. The Library of Congress.
Insects: Dobsonfly, photograph. JLM Visuals. Reproduced with permission.
Insects: Insects, fly anatomy, photograph. Hans & Cassidy. Courtesy of Gale Research.
Instinct: Instinct, young birds with mouths open, photograph. © Roy Marsch/Stock Market. Reproduced with permission.
Integrated circuit: Micro wires, silicon chip, photograph. © Andrew Syred/Science Photo Library, The National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Integrated pest management: Integrated pest management, house, pesticides, photograph. Hans & Cassidy. Courtesy of Gale Research.
Integumentary system: Human skin, diagram, photograph. Hans & Cassidy. Courtesy of Gale Research.
Interference: Interference patterns, water drops, photograph. © Martin Dohrn, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Interferometry: Interferometry, illustration. Hans & Cassidy. Courtesy of Gale Research.
Interferometry: Interferometry, diagram, mirrors, source, beam splitter, detector, illustration. Hans & Cassidy. Courtesy of Gale Research.

Interferometry: Interferometry, box with morrors, photograph. Hans & Cassidy. Courtesy of Gale Research.
Interferometry: Interferometry, box with three mirrors, photograph. Hans & Cassidy. Courtesy of Gale Research.
Interferometry: Interferometry, light going through lens, photograph. Hans & Cassidy. Courtesy of Gale Research.
interferometry: Interferometry, illustration, mirror, light source, detectot, illustration. Hans & Cassidy. Courtesy of Gale Research.

Interferon: Fermentation units, microorganisms, photograph. © S. Stammers, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Intergrated Circuit: Odometer wafer, photograph. © Adam Hart-Davis, National Audubon Society Collection/Photo Reserchers, Inc. Reproduced with permission.
Internal combustion engine: Internal combustion, diagram of engine, photograph. Hans & Cassidy. Courtesy of Gale Research.
Internal combustion engine: Internal combustion engine, illustration. Hans & Cassidy. Courtesy of Gale Research.
International Convention for Regulation of Whaling: Convention, photograph. © James Perez, Greenpeace. Reproduced with permission.
International trade in toxic waste: International trade, photograph. © J. Meier-Wiedenbach, Greenpeace. Reproduced with permission.
International trade in toxic waste: International trade, photograph. © Recio, Greenpeace. Reproduced with permission.
Interstellar Matter: Embryo stars, photograph. (c)Julian Baum/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Introduced species: House, grassy hill, photograph. JLM Visuals. Reproduced with permission.
Inventors: Goddard, Dr. Robert H. (with rocket), photograph. U. S. National Aeronautics and Space Administration.
Inventors: Daguerre, Louis, photograph of engraving. The Library of Congress.
Inventors: de Forest, Lee, photograph. The Library of Congress.
Inventors: Edison, Thomas Alva (standing at lab table), photograph. The Library of Congress.
Inventors: Fulton, Robert, sketch. The Library of Congress.
Inventors: Goodyear, Charles, photograph of sketch. The Library of Congress.
Inventors: Gutenberg, Johannes, photograph of sketch. The Library of Congress.
Inventors: Land, Edwin H., photograph. The Library of Congress.
Inventors: Libby, Willard F., photograph. The Library of Congress.
Inventors: Morse, Samuel Finley Breese (standing by invention), photograph. The Library of Congress.
Inventors: McCormick, Cyrus H., engraving. The Library of Congress.
Inventors: Whitney, Eli, (seated at a desk), photograph. The Library of Congress.
Inventors: Braille, Louis, photograph of marble bust. The Library of Congress.
Inventors, Americans: Bell, Alexander Graham, photograph. U. S. National Aeronautics and Space Administration.
Inventors, Biophysicists: Wilkins, Maurice Hugh Frederick, photograph. The Library of Congress.
Inventors, Scientists: Joliet-Curie, Frederic, photograph. The Library of Congress.
Invertebrates: Vase sponge, invertebrates, photograph. © David Mechlin/Phototake NYC. Reproduced with permission.
Invertebrates: Invertebrates, circle, photograph. Hans & Cassidy. Courtesy of Gale Research.
Invertebrates: Invertebrates, photograph. © David Mechlin/Phototake NYC. Reproduced with permission.
Ion exchange: Ion exchange, large diagram, photograph. Hans & Cassidy. Courtesy of Gale Research.
Iris: Blue flower, iris, photograph. JLM Visuals. Reproduced with permission.
Iron: Magnet seperating mixture, photograph. © Yoav Levy/Phototake NYC Reproduced with permission.
Irrigation: Trucks, watering devices, photograph. JLM Visuals. Reproduced with permission.
Irrigation: Irrigation, photograph. U. S. Geological Survey.
Island: Bahama Islands seen from space shuttle, photograph. U. S. National Aeronautics and Space Administration (NASA).
Islands: Island, Malaysia, photograph. © Ian R. Lloyd/Stock Market. Reproduced with permission.
Jaguar: Jaguar in tree, photograph. JLM Visuals. Reproduced with permission.
Jellyfish: Jellyfish, photograph. © Mark A. Johnson/Stock Market. Reproduced with permissions.
Jenner, Edward: Jenner, Edward, photograph of painting. The Library of Congress.
Jet engine: Jet engine, illustration. Hans & Cassidy. Courtesy of Gale Research Inc.
Jet engjne: Jet engine, photograph. © Joe Towers/Stock Market. Reproduced with permission.
Jewett, Frank Baldwin: Jewett, Frank Baldwin, portrait. The Library of Congress.
Joule, James Prescott: Joule, James Prescott, portrait. The Library of Congress.
Julian, Percy Lavon: Julian, Percy Lavon, (head and shoulders), portrait. The Library of Congress.
Juniper: Juniper, photograph. Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Jupiter: Surace view of Jupiter, photograph. U. S. National Aeronautics and Space Administration (NASA).
Jupiter: Jupiter, comparative view, photograph. U. S. National Aeronautics and Space Administration (NASA).
Jupiter: Jupiter, photograph. U. S. National Aeronautics and Space Administration (NASA).
Jurists: Holmes, Oliver Wendell, photograph. The Library of Congress.
Kangaroo Rat: Kangaroo Rat, photograph. U.S. Fish & Wildlife Service.
Kangaroos and Wallabies: Red kangaroo, photograph. © Leonard Lee Rue III, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Kangaroos and wallabies: Kangaroos and wauabies, photograph. © Cynthia Matthews/Stock Market. Reproduced by permission.
Kapista, Pyots: Kapista, Pyots, portrait. The Library of Congress.
Karrer, Paul: Karrer, Paul, portrait. The Library of Congress.
Karsh Topography: Pepino Hills, China, photograph. JLM Visuals. Reproduced with permission.
Kastler, Alfred: Kastler, Alfred, photograph. The Library of Congress.
Kekule von Stradoritz, August: Kekule von Stradortiz, August, portrait. The Library of Congress.
Kelly, William: Kelly, William, portrait. The Library of Congress.
Kendall, Edward C.: Kendall, Edward C., portrait. The Library of Congress.
Kendrew, John: Kendrew, John, photograph. The Library of Congress.
Kingfisher: Kingfish, rock, photograph. © Eric Hosking, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Kinglets: Kinglets, photograph. Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Kirkland's warbler: Kirtland's Warbler, photograph. © National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Kite: Kite, photograph. Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Klaproth, Martin: Klaproth, Martin, portrait.
Koala: Koala, photograph. Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Koch, Robert: Koch, Robert, photograph. The Library of Congress.
Kolliker, Rudolph Albert von: Kolliker, Rudolph Albert von, portrait. The Library of Congress.
Kornberg, Arthur: Kornberg, Arthur, portrait. The Library of Congress.
Kovalevski, Sonya Valsil: Kovalevski, Sonya Valsil, portrait. The Library of Congress.
Krebs, Hans Adolf: Krebs, Hans Adolf, photograph. The Library of Congress.
Krogh, August: Krogh, August, portrait. The Library of Congress.
Kuhn, Richard: Kuhn, Richard, portrait. The Library of Congress.
Lactic acid: Lactic acid, molecular structure, photograph. Hans & Cassidy. Courtesy of Gale Research.
Lagomorph: Jack Rabbit, photograph. JLM Visuals. Reproduced with permission.
Lagomorphs: Pika, photograph. JLM Visuals. Reproduced with permission.
Lagrange, Joseph Louis: Lagrange, Joseph Louis, portrait. The Library of Congress.
Lake: Kettle Lake, WS., photograph. JLM Visuals. Reproduced with permission.
Lamarck, Jean Baptiste: Lamarck, Jean Baptiste, portrait. The Library of Congress.
Lamb, Willis E. Jr.: Lamb, Willis E. Jr., portrait. The Library of Congress.
Lamprey: Lamprey hanging from rock, photograph. © Omikron, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Land Use: Incan terraces, photograph. JLM Visuals. Reproduced with permission.
Land use: Germantown, photograph. JLM Visuals. Reproduced with permission.
Landau, Lev Davidovich: Landau, Lev Davidovich, photograph. The Library of Congress.
Landfill: Fresh kills landfill, photograph. © Andrew Holbrooke/Stock Market. Reproduced with permission.
Landform: Landform, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Landform: Tower karst, stone forest, photograph. JLM Visuals. Reproduced with permission.
Landsteiner, Karl: Landsteiner, Karl, photograph. The Library of Congress.
Langley, Samuel: Langley, Samuel, portrait. The Library of Congress.
Langurs: Monkey, speckled langur, photograph. © Jen and Des Bartlett, National Aububon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Lanthanum: Lanthanum, photograph. © Michael W. Davidson, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Laplace, Pierre Simon: Laplace, Pierre Simon, photograph. The Library of Congress.
Large magellanic cloud: Large magellanic cloud, photograph. Royal Observatory, Edinburgh/Science Photo Library, National Audubon Society/Photo Researchers, Inc. Reproduced by permission.
Larks: Birds, Lark, photograph. © Randy Ury/Stock Market. Reproduced with permission.
Laser Rogers, Chris/Bikderberg. Laser, photograph. Stock Market. Reproduced with permissions.
Laser surgery: Cosmetic surgery, lasers, photograph. © Will & Deni McIntyre, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Laue, Max von: Laue, Max von, photograph. The Library of Congress.
Laveran, Alphonse: Laveran, Alphonse, portrait. The Library of Congress.
Lawrence, Ernest Orlando: Lawrence, Ernest Orlando, photograph. The Library of Congress.
LCD: Liquid crystal display, illustration, photograph. Hans & Cassidy. Courtesy of Gale Research.
Lead: Lead, photograph. © Chris Jones/The Stock Market. Reproduced with permission.
Leaf: Electron micrograph, tobacco leaf, photograph. © Dr. Jeremy Brugess/Science Photo Library, National Audubon Society Collection/ Photo Researchers, Inc. Reproduced with permission.
Lecithin: Molecular structure of lecithin, photograph. Hans & Cassidy. Courtesy of Gale Research.
Lecithin: Lecithin, beads, photograph. Hans & Cassidy. Courtesy of Gale Research.
LED: Circuit board, LED, photograph. © Peter Steiner/Stock Market. Reproduced with permission.
LED: LED display, magnified image, photograph. © Alfred Pasieka/Science Photo Library, The National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
LED: LEDRE, gold connecting wire, photograph. Hans & Cassidy. Courtesy of Gale Research.
Lederberg, Joshua: Lederberg, Joshua, photograph. The Library of Congress.
Lederman, Leon Max: Lederman, Leon Max, photograph. The Library of Congress.
Lee, Tsung Dao and Yang, Chen Ning: Lee, Tsung Dao and Yang, Chen Ning, portrait. The Library of Congress.
Leeuwenhoek, Antonj van: Leeuwenhoek, Antonj van, photograph. The Library of Congress.
Legumes: Plant, legumes, photograph. JLM Visuals. Reproduced with permission.
Legumes: Green bean, phaseolus vulgaris, photograph. JLM Visuals. Reproduced with permission.
Leibniz, Gottried: Leibniz, Gottfried, portrait. The Library of Congress.
Lemurs: Lemurs, photograph. © Mark Phillips, Photo Researchers, Inc. Reproduced with permission
Lenard, Philipp E.A. von: Lenard, Philipp E.A. von, portrait. The Library of Congress.
Lens: Lens, light going through, photograph. Hans & Cassidy. Courtesy of Gale Research.
Lens: Lens, five illustrations of light going through, photograph. Hans & Cassidy. Courtesy of Gale Research.
Leopard: Leopard walking across sand, photograph. © Tom Brakerfield/Stock Market. Reproduced with permission.
Leprosy: Foot with leprosy, photograph. © CNRI/Phototake NYC. Reproduced with permission.
Lice: Lous, photograph. JLM Visuals. Reproduced with permission.
Lichens: Red flower plants, lichens, photohraph. JLM Visuals. Reproduced with permission.
Liebig, Jushes von: Liebig, Jushes von, portrait. The Library of Congress.
Ligand: Ligand, ammonia, silver, photograph. Hans & Cassidy. Courtesy of Gale Research.
Ligand: Ligand, two illustrations, photograph. Hans & Cassidy. Courtesy of Gale Research.
Ligand: Ligand, three illustrations, linear, square planner, octahedral, photograph. Hans & Cassidy. Courtesy of Gale Research.
Ligand: Ligand, three illustrations, photograph. Hans & Cassidy. Courtesy of Gale Research.
Ligand: Ligand, two large molecular structures, EDTA, illustration. Hans & Cassidy. Courtesy of Gale Research.
Ligand: Ligand, large molecular structure, illustration. Hans & Cassidy. Courtesy of Gale Research.
Lightning and Thunder: Lightening, Tanworth, photograph. © Gordon Garrado/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. n Reproduced with permission.
Lilac: Lilac. James Lee Sikkema. Reproduced by permission.

Lilienthal, Otto: Lilienthal, Otto, portrait. The Library of Congress.
Lilienthal, Otto
Lily family: Lily, photograph. James Lee Sikkema. Reproduced by permission.
Lily family: Lily, photograph. James Lee Sikkema. Reproduced by permission.
Lily family: Lily, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission
Linear Accelerator: Linear accelorator, photograph. © David Parler, National Audubon Society Collection/Photo Researchers Inc. Reproduced with permission.
Linnaeus, Carl: Linnaeus, Carl, photograph. The Library of Congress.
Lion Tamarins: Lion Tamarins, photograph. © Jeanne White , National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Lion-tailed macaque: Lion-tailed macaque, photograph. © Tom McHugh, Photo Researchers, Inc. Reproduced with permission
Liquid crystals: Polarized light micrograph, water crystals, photograph. © James Bell/Science Photo Library, The National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Lister, Joseph: Lister, Joseph, portrait. The Library of Congress.
Lithography: Lithographic books, photograph. © Morris Lane/Stock Market. Reproduced with permission.
Lithrotripsy: Lithothripton, photograph. © S.I.U.,National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Liverwort: Broccoli-like plant, liverwort, photograph. JLM Visuals. Reproduced with permission.
Livestock : Chicken and man on tractor field, photograph. © Herbert Wexler, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Livestock: Livestock, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Lobster: Lobster, photograph. JLM Visuals. Reproduced with permission.
Lock and key: Lock and key, line drawing. Hans & Cassidy. Courtesy of Gale Research.
Locks: Ships, Miraflores lock, photograph. © Will and Deni McIntyre, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Locus: Locus, three line graphs, photograph. Hans & Cassidy. Courtesy of Gale Research.
Locus: Locus figure, four circles, photograph. Hans & Cassidy. Courtesy of Gale Research.
Locus: Locus figure, photograph. Hans & Cassidy. Courtesy of Gale Research.
Lodge, Oliver Joseph: Lodge, Oliver Joseph, portrait. The Library of Congress.
Loewi, Otto: Loewi, Otto, portrait. The Library of Congress.
Logarithms: Logarithms, illustration. Hans & Cassidy. Courtesy of Gale Research.
Loons Hosking, Eric.: Loon, photograph. © Eric Hosking, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Lorentz, Hendrik Antoon: Lorentz, Hendrik Antoon, portrait. The Library of Congress.
Lorises: Slender loris, photograph. © Jen and Des Bartlett, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Los Angeles Basin: Los Angeles Basin, photograph. © Ron Romanosky, Greenpeace. Reproduced with permission.
Love Canal, NY: Love Canal, NY, photograph. © Lisa Bunin/Greenpeace 1980. Reproduced with permission.
Lovelace, Augusta: Lovelace, Augusta, portrait.
Lungfish: Lungfish, prehistoric, living, photograph. Hans & Cassidy. Courtesy of Gale Research.
Lungfish: Lungfish, illustration. Hans & Cassidy. Courtesy of Gale Research.
Lwoff, Andre: Lwoff, Andre, photograph. The Library of Congress.
Lyell, Charles Sir: Lyell, Charles Sir, photograph of drawing. The Library of Congress.
Lyme disease: Lyme disease, deer-tick carrier, photograph. © Spielman/CNRI/Phototake NYC. Reproduced with permission.
Lynen, Feodor: Lynen, Feodor, portrait. The Library of Congress.
Lyre Birds: Male lyre in forest foilage, photograph. © John R. Brownlie, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Macaques: Macaques, photograph. © Charles H. Southwick. Reproduced with permission.
Mach number: Mach Number, orbit, photograph. Hans & Cassidy. Courtesy of Gale Research.
Mach number: Mach Number, diagram, photograph. Hans & Cassidy. Courtesy of Gale Research.
Machine Tools: Machine tools, shaping wood, photograph. © Pedro Coll/Stock Market. Reproduced with permission.
Machine tools: Water knife, machinery, photograph. © Account Phototake/Phototake NYC. Reproduced with permission.
Machines, simple: Lever and fulcrum, machines, photograph. © David R. Frazier/ Photolibrary, The National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Mackerel: Mackerel, swimming, Largo, Florida, photograph. © Fred McConnaughey, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Macleod, John James Richard: Macleod, John James Richard, portrait. The Library of Congress.
MAGLEV: Front of supertrain, photograph. © Account Phototake/Phototake, NYC. Reproduced with permission.
Magma: Lava from Kileuea, HA., photograph. JLM Visuals. Reproduced with permission.
Magnesium: Magnesium burning, photograph. © Yoav Levy/Phototake NYC Reproduced with permission.
Magnetic levitation: Magnet levitation, photograph. © Philippe Plailly/Science Photo Library, The National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Magnetic recording/audiocassette: Magnetic recording, diagram, photograph. Hans & Cassidy. Courtesy of Gale Research.
Magnetic recording/audiocassette: Magnetic recording, diagram of tape recorder, illustration. Hans & Cassidy. Courtesy of Gale Research.

Magnetism: Horseshoe magnet, computer graphic, photograph. © Alfred Pasieka/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Magnetosphere: Magnetosphere, diagram, photograph. Hans & Cassidy. Courtesy of Gale Research.
Magnolia: Magnolia, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Maidenhair fern: Maidenhair fern, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Malaria: Malaria, moquito, human, photograph. Hans & Cassidy. Courtesy of Gale Research.
Malayan tapir: Malayan tapir, photograph. © W. Ambler, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Malnutrition: Malnutrition, child, photograph. © Bruce Brander, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Manatee: Young manatee, Crystal River, Florida, photograph. © Douglas Faulkner, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Manatee: Manatee, photograph. © U.S. Fish & Wildlife Service.
Mangrove swamp: Mangrove swamp, photograph. M. Woodbridge Williams, National Park Service.
Mangrove tree: Small group of trees, mangrove trees, photograph. JLM Visuals. reproduced with permission.
Manned wolf: Manned wolf, forest, photograph. © Francois Gohier, Photo Researchers, Inc. Reproduced with permission
Map: Map, Texas, photograph. Hans & Cassidy. Courtesy of Gale Research.
Maples: Sugar maple, photograph. James Lee Sikkema. Reproduced by permission.
Maples: Maples, photograph. James Lee Sikkema. Reproduced with permission.
Marconi, Guglielmo: Marconi, Guglielmo, photogtraph. The Library of Congress.
Marijuana: Compressed brick of marijuana, photograph. © Tom McHugh, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Marine Biologists, Environmentalists: Carson, Rachel, photograph. The Library of Congress.
Marine Pollution: Marine Pollution, photograph. © Robert Visser, Greenpeace. Reproduced with permission.
Marine pollution: Marine pollution, photograph. © U.S. Fish & Wildlife Service.
Marlin: Marlin, photograph. © Darrill Jones/Stock Market. Reproduced with permission.
Marmoset: Marmoset, photograph. © Howard Earl Uible, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Marmot: Marmot, photograph. JLM Visuals. Reproduced with permission.
Mars: Mars, steller view, photograph. NASA. Reproduced with permission.
Mars: Mars, surface view, photograph. NASA. Reproduced with permission.
Mars: Martian crater, photograph. NASA. Reproduced with permission.
Mars: Face of Mars taken by Viking I, photograph. U. S. National Aeronautics and Space Administration (NASA).
Mars: Top of Mars as seen from Viking I, photograph. U. S. National Aeronautics and Space Administration (NASA).
Mass Production: Doughnut manufacturing company, photograph. © Chris Jones/Stock Market. Reproduced with permission.
Mass spectrometry: Spectrometer, photograph. © Geoff Tompkinson/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Mass Transportation: Mass transportation, New York subway, photograph. © John Madere/Stock Market. Reproduced with permission.
Mass wasting: Landslide, CA., photograph. JLM Visuals. Reproduced with permission.
Mass wasting: Avalanche, photograph. © Ned Gillette/Stock Market. Reproduced with permissions.
Mathematicians: Babbage, Charles, engraving. The Library of Congress.
Mathematicians: Hopper, Grace, photograph. The Library of Congress.
Mathematicians, Inventors: Banneker, Benjamin, drawing. Source unknown.
Matter: Silica aergel, photograph. © Science Source,National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Matthews, Alva T.: Matthews, Alva T., portrait. The Library of Congress.
Maury, Matthew Fontain: Maury, Matthew Fontain, photograph of engraving. The Library of Congress.
Maxim, Hiram Stevens: Maxim, Hiram Stevens, portrait. The Library of Congress.
Maxima and minima: Maxima and minima, graph, photograph. Hans & Cassidy. Courtesy of Gale Research.
Maxima and minima: Maxima and minima, "v" graph, photgraph. Hans & Cassidy. Courtesy of Gale Research.
Maxwell, James Clerk: Maxwell, James Clerk, photograph of engraving. The Library of Congress.
Mayer, Julius Robert: Mayer, Julius Robert, portrait. The Library of Congress.
Mayflies: Mayflies, photograph. © Robert C. Hermes,National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Mays, Benjamin E.: Mays, Benjamin (seated in chair), photograph. AP/Wide World Photos. Reproduced by permission.
McCarthy, John: McCarthy, John, portrait. The Library of Congress.
McCollum, Elmer Verner: McCollum, Elmer Verner, portrait. The Library of Congress.
McMillan, Edwin M.: McMillan, Edwin M., portrait. The Library of Congress.
Measurement Systems: Scale, copper, photograph. © Thomas Ernsting/Stock Market. Reproduced with permissions.
Measurement systems: Measurement systems, illustration. Robert L. Wolke. Reproduced with permissions.
MED 1315: Dissection during the Middle Ages, portrait. The Library of Congress.
MED 1388: Richard II, portrait. The Library of Congress.

MED 1491: Doctor treating plague victim, portrait. The Library of Congress.
MED 1517: First picture ever made of an amputation, portrait. The Library of Congress.
MED 1535: Cordus, Valerius, portrait. The Library of Congress.
MED 1700: Princeps, Editio, portrait. The Library of Congress.
MED 1700: Ramazzini, Bernardino, portrait. The Library of Congress.
MED 1774: Percival, Thomas, portrait. The Library of Congress.
MED 1796: Jenner, Edward , portrait. The Library of Congress.
MED 1800: Waterhouse, Benjamin, portrait. The Library of Congress.
MED 1809: McDowell, Ephraim, portrait. The Library of Congress.
MED 1849: Women in medicine, portrait. The Library of Congress.
MED 1851: Graefe, Albrecht von, portrait. The Library of Congress.
MED 1862: Pean, Jules, portrait. The Library of Congress.

MED 1870: Billroth, Theodor, portrait. The Library of Congress.
MED 1879: Billings, John Shaw, portrait. The Library of Congress.
MED 1881: Barton, Clara, photograph of portrait. The Library of Congress.
MED 1882: Blood transfusion, portrait. The Library of Congress.
MED 1884: Freud, Sigmund, portrait. The Library of Congress.
MED 1885: Trudeau, Edward, portrait. The Library of Congress.
MED 1949: DDT, portrait. The Library of Congress.
MED 1949: DDT, portrait. The Library of Congress.
MED 75: Dioscorides, portrait. The Library of Congress.

MED 75: Dioscorides, portrait. The Library of Congress.

Medawar, Peter Brian: Medawar, Peter Brian, photograph. The Library of Congress.
Medicos: Hippocrates of Cos, photograph of bust. The Library of Congress.
Medicos: Blackwell, Elizabeth, photograph. The Library of Congress.
Medicos, Toxicologists: Hamilton, Alice, photograph. The Library of Congress.
Meitner, Lise: Meitner, Lise, photograph. The Library of Congress.
Membranes: Freeze fracture across wall of membrane, photograph. © Dr. Dennis Kunkel/Phototake NYC. Reproduced with permission.
Mendeleev, Dmitry Ivanovich: Mendeleev, Dmitry Ivanovich, photograph. The Library of Congress.
Mendelian laws of inheritance: Mendelian laws, the law of segregation, photograph. Hans & Cassidy. Courtesy of Gale Research.
Mendelian laws of inheritance: Mendelian law, law of independent assortment, illustration. Hans & Cassidy. Courtesy of Gale Research.

Mendelian laws of inheritance: Mendelian laws of inheritance, illustration. Hans & Cassidy. Courtesy of Gale Research.
Menstrual cycle: Mestrual cycle, uterine cycle, hormone level, ovarian cycle, illustration. Hans & Cassidy. Courtesy of Gale Research.
Mercer, John: Mercer, John , portrait. The Library of Congress.
Mercury: Mercury, photograph. U. S. National Aeronautics and Space Administration (NASA).
Mercury: Mercury, surface, photograph. U. S. National Aeronautics and Space Administration (NASA).
Mercury: Droplets of mercury, photograph. © Dr. Jeremy Burgess/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Mercury: Face of Mercury taken by Mariner 10, photograph. U. S. National Aeronautics and Space Administration (NASA).
Mercury: Surface of Mercury, photograph. U. S. National Aeronautics and Space Administration (NASA).
Mercury (planet): Mercury, diagram of orbit, photograph. Hans & Cassidy. Courtesy of Gale Research.
Mercury (planet): Mercury, interior, photograph. Hans & Cassidy. Courtesy of Gale Research.
Mergenthaler, Ottmar: Mergenthaler, Ottmar, portrait. The Library of Congress.
Metabolism: Metabolism, illustration. Robert L. Wolke. Reproduced with permission.
Metal: Scrap metal pile, photograph. © Wes Thompson/Stock Market. Reproduced with permission.
Metal Production: Metal production, steel worker, photograph. © John Olson/Stock Market. Reproduced with permission.
Metamorphic Rock: Gneiss, metamorphic rocks, Nevada, photograph. JLM Visuals. Reproduced with permission.
Metamorphism: Metamorphism, Granite, Obsidian, photograph. © John Buitenkant, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Metamorphosis: Monarch butterfly, metamorphosis, phototgraph. © Nelson-Bohart & Associates/Phototake NYC. Reproduced with permission.

Metchnikoff, Elic: Metchnikoff, Elic, portrait. The Library of Congress.
Meteors and Meteorites: Crater, photograph. U. S. National Aeronautics and Space Administration (NASA).
Meteors and meteorites: Meteors and meteorides, earth's position, meteoroid stream, illustration. Hans & Cassidy. Courtesy of Gale Research.

Meteors and meteorites: Meteors and meteorites, diagram, observer, illustration. Hans & Cassidy. Courtesy of Gale Research.
Meteors and meteorites: Meteors and meteorites, orbit diagram, photograph. Hans & Cassidy. Courtesy of Gale Research.
Methanol (wood alcohol): Computer model, methanol, photograph. © Ken Eward/Science Source, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Mexico City: Mexico City, photograph. © Andrew Davis, Greenpeace. Reproduced with permission.
Meyerhof, Otto: Meyerhof, Otto, portrait. The Library of Congress.
Mice: Mice in wheatfield, photograph. © Eric Hosking, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Michelson, Albert: ichelson, Albert, photograph. The Library of Congress.
Microbiologists: Theiler, Max, photogtaph. The Library of Congress.
Microbiologists: Watson, James Dewey, photograph. The Library of Congress.
Microphone: Microphone, line drawing. Hans & Cassidy. Courtesy of Gale Research.
Microscope Compound : Microscope, student, photograph. Research. Carolina Biological Supply. (c) Carolina Biological Supply Company/Phototake NYC. Reproduced with permission.
Microwave oven: Microwave oven, diagram, photograph. Hans & Cassidy. Courtesy of Gale
Microscopy: Atomic force micrograph, photograph. © Philippe Plailly, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Microtechnology: Electronics, circut board, satellite spacecraft transmitter, photograph. © Brownie Harris/Stock Market. Reproduced with permission.
Microwave communicator: Microwave communication tower, Munich Germany, photograph. (c) Tony Craddock, National Audubon Society Collection/Photo Researchers,Inc. Reproduced with permission.
Microwave oven: Microwave oven, diagram, photograph. Hans & Cassidy. Courtesy of Gale Research.
Microwave oven: Microwave oven, diagram, photograph. Hans & Cassidy. Courtesy of Gale Research.
Microwave oven: Microwave oven, diagram, photograph. Hans & Cassidy. Courtesy of Gale Research.
Migraine: Migraine, man's head, symptoms, illustration. Hans & Cassidy. Courtesy of Gale Research.
Migration: Migration, photograph. © U.S. Fish & Wildlife Service.
Migration: Migration, photograph. © U.S. Fish & Wildlife Service.
Milkweeds: Plant, milkweed, photograph. JLM Visuals. reproduced with permission.
Milkweeds: Milkweeds, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Milky Way: Milky Way, photograph. © Fred Espenak, Science Photo Library. Reproduced with permission.
Millikan, Robert A.: Millikan, Robert A., photograph The Library of Congress.
Millipedes: Millipedes, photograph. JLM Visuals. Reproduced with permission.
Mimicry: Indian Leaf Butterfly, photograph. © ZEFA Germany 1994/Stock Market. Reproduced with permission.
Minerals: Minerals, tarzanite, photograph. U. S. National Aeronautics and Space Administration (NASA).
Minerals: Rose quartz, photograph. U. S. National Aeronautics and Space Administration (NASA).
Mining: Strip mining, photograph. © Chris Jones/Stock Market. Reproduced with permission.
Mining: Men in a trolley, portrait. The Library of Congress.
Mink: Mink, photograph. © Nancy Sanford/Stock Market. Reproduced with permission.
Minnows: Shiners, photograph. JLM Visuals. Reproduced with permission.
Minor Planets (asteroids): Minor planets, graph, distance vs. number of asteroids, photograph. Hans & Cassidy. Courtesy of Gale Research.

Minor Planets (asteroids): Minor planets, small diagram of orbits, photograph. Hans & Cassidy. Courtesy of Gale Research.
Minot, George Richards: Minot, George Richards, portrait. The Library of Congress.
Mint family: Plant, mint stems, photograph. JLM Visuals. Reproduced with permission.
Mint family: Mint family, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Mirror: Mirror, diagram, photograph. Hans&Cassidy. Courtesy of Gale Research.
Mirrors: Mirrors, photograph. © Richard Nowitz/Phototake NYC. Reproduced with permission.
Mirrors: Mirrors, line drawing. Hans & Cassidy. Courtesy of Gale Research.
Mirrors: Mirrors, line drawing. Hans & Cassidy. Courtesy of Gale Research.
Mistletoe: Plant, mistletoe, photograph. JLM Visuals. Reproduced with permission.
Mites: Mites, photograph. © Dennis Kunkel /Phototake NYC. Reproduced with permission. Mitosis: Mitosis, illustration. Hans & Cassidy. Courtesy of Gale Research.
Mitosis: Mitosis, illustration. Hans & Cassidy. Courtesy of Gale Research.
Mixture, chemical: Chemical mixture, photograph. © Phototake NYC Reproduced with permission.
Mobius strip: Mobius strip, rectangle, photograph. Hans & Cassidy. Courtesy of Gale Research.
Mobius strip: Mobius strip, loop, illustration. Hans & Cassidy. Courtesy of Gale Research.
Mockingbirds and Thrashers: Mockingbirds and thrashers, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.

Mockingbirds and Thrashers: Mockingbirds and thrashers, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.

Mole: Mole crawling through grass, photograph. © Zefa Germany/Stock Market. Reproduced with permission.
Mole: Mole quantities of elements, photograph. © Yoav Levy/Phototake NYC Reproduced with permission.
Mole Rat: Mole rat, photograph. © Tom McHugh, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Molecule: Molecule, illustration. Robert L. Wolke. Reproduced with permission.
Molecule: Molecule, six unions, photograph. Hans & Cassidy. Courtesy of Gale Research.
Molecule: Molecule, molecular structure, ethyl alcohol, methyl ether, photograph. Hans & Cassidy. Courtesy of Gale Research.
Molecule: Molecular, diagrams of e-, photograph. Hans & Cassidy. Courtesy of Gale Research.
Mollusks: File Shell, photograph. JLM Visuals. Reproduced with permission.
Mollusks: Phillipine nudibranch, photograph. JLM Visuals. Reproduced with permission.
Monge, Gaspard: Monge, Gaspard, portrait. The Library of Congress.
Mongoose: Banded mongooses, photograph. © Leonard Lee Rue III, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Monitor Lizards: Komodo dragons, goat carcass, photograph. © Jen and Des Bartlett, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Monkeys: Spider monkey, photograph. © Mark D. Phillips, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Monoculture: Wheat field, photograph. © National Aububon Society Collection/Photo Reseerchers, Inc. Reproduced with permission.
Monod, Jacques Lucien: Monod, Jacques Lucien, portrait. The Library of Congress.
Monosodium glutamate (MSG): Monosodium glutamate, photograph. © Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Montgolfier, Jacques and Joseph: Montgolfier, Jacques and Joseph, portrait. The Library of Congress.
Moon: Moon, photograph. U. S. National Aeronautics and Space Administration (NASA).
Moon: Moon surface, photograph. U. S. National Aeronautics and Space Administration (NASA).
Moon: Outer rim of moon, photograph. U. S. National Aeronautics and Space Administration (NASA).
Moon: Moon crater, photograph. U. S. National Aeronautics and Space Administration (NASA).
Moon: Memorial plaque on moon's surface, photograph.U. S. National Aeronautics and Space Administration (NASA).
Moon: Expanse of MA, Conn, R.I. taken from moon, photograph. U. S. National Aeronautics and Space Administration (NASA).
Moose: Moose in pond eating, photograph. © Robert Essel/Stock Market. Reproduced by permission.
Morgan, Thomas Hunt: Morgan, Thomas Hunt, photograph. The Library of Congress.
Morley, Edward William: Morley, Edward William, portrait. The Library of Congress.
Morse, Samuel F. B.: Morse, Samuel F. B., portrait. The Library of Congress.
Mosquito: Mosquito, human skin, photograph. © Rod Planck, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Moss: Moss, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Moss: Moss, life cycle, photograph. Hans & Cassidy. Courtesy of Gale Research.
Moths: Moths, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Moths: Moths, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Motion: Pendulum, photograph. © Yoav Levy/Phototake NYC. Reproduced with permission.
Mount Pinatubo: Mount Pinatubo, photograph. © T. J. Casadevall, U. S. Geological Survey Photographic Library Denver, CO. Reproduced with permission.
Mount St. Helens: Mount St. Helens, photograph. U. S. Geological Survey.
Mount St. Helens: Eruption of Mt. St. Helens, photograph. U. S. Geological Survey.
Mountain: Folding in mountain, photograph. JLM Visuals. Reproduced with permission.
Mountain Pygmy-Possum: Mountain Pygmy-Possum, photograph. © OMIKRON, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Mountain Zebra: Mountain Zebra, photograph. © Michele Burgess/Stock Market. Reproduced with permission.
Mousebirds: Mousebirds, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Muir, John: Muir, John, portrait. The Library of Congress.

Mulberry family: Tree, Mulberry, photograph. JLM Visuals. Reproduced with permission.
Muller, Hermann Joseph: Muller, Hermann Joseph, photograph. The Library of Congress.
Mulliken, Robert S. Mulliken, Robert S., portrait. The Library of Congress.
Municipal Solid Waste: Municipal Solid Waste, photograph. © Robert Visser, Greenpeace. Reproduced with permission.
Murdock, William: Murdock, William, portrait. The Library of Congress.
Murphy, William P.: Murphy, William P., portrait. The Library of Congress.
Musk oxen: Musk oxen, photograph. JLM Visuals. Reproduced with permission.
Muskrat: Muskrat, tree trunk, photograph. © Leonard Lee Rue III, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Mustard family: Mustard family, photograph. James Lee Sikkema. Reproduced by permission.
Mustard family: Mustard family, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced by permission.
Mutation: Six-legged frog, photograph. JLM Visuals. Reproduced by permission.
Mutualism: Claener shrimp, cleaner moray, photograph. JLM Visuals. Reproduced with permission.
Muybridge, Eadweard James: Muybridge, Eadweard James, portrait. The Library of Congress.
Mycorrhiza: Mycorrhiza, ectotrophic host roots, photograph. © Biophoto Associates, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Mynah Bird: Bird, Mynah, photograph. © S. Brookens/Stock Market. Reproduced with permission.
Myrtle family: Eucalyptus tree, Australia, photograph. JLM Visuals. Reproduced with permission.
Nanotechnology: Nanotechnology, tiny chip on hands, photograph. © James King-Holmes/Science Photo Library, The National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Nanotechnology: Nanotechnology, flow chart, photograph. Hans & Cassidy. Courtesy of Gale Research.
Napier, John: Napier, John, portrait. The Library of Congress.
National forest: National forest, photograph. © Samual Frear/U. S. Forest Service.
National lake shore: National lake shore, photograph. © Richard Frear, National Park Service. Reproduced with permission.
National lake shore: National lake shore, photograph. © Richard Frear, National Park Service. Reproduced with permission.
National park: National park, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
National park: National Park, photograph. U. S. Geological Survey Photographic Library Denver, CO.
National seashore: National seashore, photograph. © M. Woodbridge Williams, National Park Service. Reproduced with permission.
National wildlife refuge: National wildlife refuge, photograph. U.S. Fish & Wildlife Service.
Natta, Giulio: Natta, Giulio, portrait. The Library of Congress.
Natural Fibers: Natural fibers, silk fibers, photograph. © Dr. Dennis Kunkel/Phototake NYC. Reproduced with permission.
Natural Gas: Gas well, photograph. © Byron F. Peterson/Stock Market. Reproduced with permission.
Neptune: Neptune, photograph. U. S. National Aeronautics and Space Administration (NASA).
Neptune: Neptune, photograph. U. S. National Aeronautics and Space Administration (NASA).
Neptune: Neptune, graph, year vs. latitude, photograph. Hans & Cassidy. Courtesy of Gale Research.
Neptune: Neptune, drawing, photograph. Hans & Cassidy. Courtesy of Gale Research.
Neptune: Neptune, two diagram's of orbit, photograph. Hans & Cassidy. Courtesy of Gale Research.
Nernst, Walther: Nernst, Walther, photograph of a drawing. The Library of Congress.
Neuron: SEM, nerve cells, photograph. © Secchi-Lecague/Roussel-UCLAF/CNRI/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Neuron: Neuron, diagram, photograph. Hans & Cassidy. Courtesy of Gale Research.
Neutron star: Neutron star, photograph. U. S. National Aeronautics and Space Administration (NASA).
Neutron star: Neutron star, diagram, photograph. Hans & Cassidy. Courtesy of Gale Research.
Newell, Allen: Newell, Allen, photograph. Carnegie-Mellon University Photos. Reproduced with permission.
Newt: Western newt, leaf, photograph. © A.W. Ambler, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Nickel: Small pieces of nickel, photograph. © Russ Lappa/Science Source, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Nightshade family: Tobacco field, photograph. JLM Visuals. Reproduced by permission.
Nightshade family: Nightshade family, photograph. James Lee Sikkema. Reproduced by permission.
Nightstars and Frogmouths: Frogmouth, photograph. JLM Visuals. Reproduced with permission.
Niobium: Niobium, photograph. © Russ Lappa/Science Source,National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Nirenberg, Marshall Warren Nirenberg, Marshall Warren, photograph The Library of Congress.
Nitric acid: Chemical reaction, nitric acid, photograph. © LevyYoav/Phototake NYC. Reproduced with permission.
Nitrogen: Computer graphic, molecular structure of nitrogen, photograph. © Clive Freeman,The Royal Institution/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Nitrogen cycle: Nitrogen cycle, environment, photograph. Hans & Cassidy. Courtesy of Gale Research.
Nitrogen fixation: Nitrogen fixation, bacteria, plants, photograph. © Adam Hart-Davis, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Nitrogen fixation: Nitrogen fixation, photograph. National Center for Atmospheric Research/University Corporation for Atmospheric Research/National Science Foundation 1112. Reproduced with permission.
Non-point source: Non point Source, fram, city, photograph. Hans & Cassidy. Courtesy of Gale Research.
North America: View of North, Centrak America from space, photograph. © George Diebold/Stock Market. Reproduced with permission.
North America: North America, illustration. Hans & Cassidy. Courtesy of Gale Research.
North, Simeon: North, Simeon , portrait. The Library of Congress.
NorthAmerica: North America, map, photograph. Hans & Cassidy. Courtesy of Gale Research.
Northern spotted owl: Northern spotted owl, photograph. © U.S. Fish & Wildlife Service.
Northrop, John Howard: Northrop, John Howard, portrait. The Library of Congress.
Nova: Novi Cygni, photograph. © Space Telescope Science Institure/NASA/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Nuclear fission: Nuclear chain reaction, illustration. Robert L. Wolke. Reproduced by permission.
Nuclear fission: Nuclear fission, illustration. Robert L. Wolke. Reproduced with permission.
Nuclear Fusion: Nuclear Fusion research, photograph. © Novosti Press Agency, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Nuclear magnetic resonance: Nuclear magnetic resonance (NMR). © Jean Claude Revy/Phototake NYC. Reproduced with permission.
Nuclear power plant: Nuclear power plant, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Nuclear reactor: Nuclear reactor, photograph. © U.S. Dept. of Eng National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Nuclear weapons: Atom bomb blast, Nagasaki, 1945, photograph. © Scott Camazine, The National Audubon Society Collection/Photo Researchers, Inc. Reproduced by permission.
Nuclear winter: Nuclear winter, photograph. National Center for Atmospheric Research/University Corporation for Atmospheric Research/National Science Foundation 1230. Reproduced with permission.
Numbat: Numbat, photograph. © John Cancalosi. Reproduced with permission.
Nuthatches: Nuthatches, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Nutrition: Nutrition, four basic food groups, photograph. © Michael A. Keller/Stock Market. Reproduced with permission.
Nylon: Nylon fibers, photograph. © Chael Siegel/Phototake NYC Reproduced with permission.
Oaks: Oaks, photograph. Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Ocean: Grand Cayman Ocean, photograph. © David Stoecklein/Stock Market. Reproduced with permission.
Ocean Dumping Ban Act: Ocean Dumping Ban Act, photograph. Greenpeace. Reproduced with permission.
Ocean Sunfish: Ocean sunfish, photograph. © Gregory Ochocki, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Oceanographers: Cousteau, Jacques, photograph. The Library of Congress.
Oceanography: Oceanography, photograph. U. S. Geological Survey Photographic Library Denver, CO.
Oceanography: Oceanography, photograph. © H. Chezar/U. S. Geological Survey Photographic Library Denver, CO.
Ochoa, Severo: Ochoa, Severo, photograph. The Library of Congress.
Octopus: Octopus, photograph. JLM Visuals. Reproduced with permission.
Oersted, Hans Christian: Oersted, Hans Christian, portrait. The Library of Congress.
Ohm, Georg Simon: Ohm, Georg Simon, portrait. The Library of Congress.
Oil Drilling: Drilling rig for oil, photograph. © David Halpern, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Oil refining: Oil refining, photograph. © Roy Morsch/Stock Market. Reproduced with permission.
Oil spill: Bird soaked in oil, Iraq oil spill, photograph. © Wesley Bocxe, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Oil Spills: Oil Spills, photograph. © J. B. Diederich/Stock Market. Reproduced with permission.
Okapi: Adult male okapi, phototgraph. © Tom Brakerfield/Stock Market. Reproduced with permission.
Old growth forest: Douglas fir forest, photograph. © Tom & Pat Lesson, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Old-growth forests: Old-growth forests, photograph. © M. Woodbridge Williams, National Park Service, Harpers Ferry Center.
Old-growth forests: Old growth forset, illustration, photograph. Hans & Cassidy. Courtesy of Gale Research.
Olive family: Olive trees, photograph. JLM Visuals. Reproduced with permission.
Omnivore: Omnivore, photograph. © U.S. Fish & Wildlife Service.
Oort, Jan Hendrix: Oort cloud, photograph. © Dr. Seth Shostak/ Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Open heart surgery: Open heart surgery, photograph. © Martin Dohrn, National Audubon Society Collection/Photo Researchers, Inc. Reproduced by permission.
Opossum: Oppossum, photograph. © Jen and Des Bartlett, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Optical data storage: Optical computer designer, photograph. © David Parker/Science Photo Library, The National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Orangutan: Orangutan, photograph. © Planet Earth. Reproduced with permission.
Orchid family: Vanilla plant, photograph. JLM Visuals. Reproduced with permission.
Orchid family: Orchid family, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Ore: Ore sample, photograph. © Paolo Koch, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission
Ore: Stribnite with quartz, photograph. U. S. National Aeronautics and Space Administration (NASA).
Organic farming: Organic farming, illustrations, photograph. Hans & Cassidy. Courtesy of Gale Research.
Orioles: Orioles, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Orogeny: Mt. Sopris, Aspen Colorado, photograph. © Art Bileten, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Oryx: Herd of Oryx, photograph. © Phototake NYC. Reproduced with permission.
Oscillations: Pendulum, oscillations, photograph. © James Steveson, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Oscilloscope: Oscilloscope, photograph. © David Parker/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Osmosis: Osmosis, illustration, magnifying glass, photograph. Courtesy of Gale Research.
Osmosis: Osmosis,two magnified views, photograph. Hans & Cassidy. Courtesy of Gale Research.
Osteoporosis: Electron micrograph, spongy bone, photograph. © Prof. P. Motta/Dept. of Anatomy/University "La Sapienza, Rome, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Ostwald, Friedrich Wilhelm: Ostwald, Friedrich Wilhelm, portrait. The Library of Congress.
Otters: Male, female sea otter, photograph. © Karl W. Kenyon, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Outcrop: Outcrop, photograph. Courtesy of U. S. Forest Service.
Overfishing: Overfishing, photograph. © Robert Visser, Greenpeace. Reproduced with permission.
Overgrazing: Overgrazed land, Turkey, photograph. JLM Visuals. Reproduced with permission.
Overhunting: Overhunting, photograph. Western History Collection, Denver Public Library. Reproduced with permission.
Oviparous: Rainbow trout eggs, photograph. JLM Visuals. Reproduced with permission.
Owls: Owls, photograph. Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Owls: Owls, photograph. Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Oxalic Acid: Oxilac acis crystals, photograph. © John Hendry/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Oxalic acid: Oxalic acid, COOH - COOH, photograph. Reproduced with permission. Courtesy of Gale Research.
Oystercatchers: Oyster catcher, photograph. JLM Visuals. Reproduced with permission.
Ozone layer depletion: Ozone layer depletion, photograph. © Greenpeace. Reproduced with permission.
Ozone layer depletion: Ozone depletion, rays being blocked, rays going through, photograph. Hans & Cassidy. Courtesy of Gale Research.

Pacemaker: Pacemakers, photograph. © Eamonn McNulty, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Pacemaker, Medical devices Pacemaker, photograph. The Library of Congress.
Palade, George: Palade, George, portrait. The Library of Congress.
Paleoanthropologists, Conservationists: Leakey, Louis, photograph. The Library of Congress.
Paleobotany: Fossillized imprints of plants, photograph. JLM Visuals. Reproduced with permission.
Paleontologists: Simpson, George Gaylord, photograph The Library of Congress.
Paleontology: Dinosaur paleontology, photograph. © Philippe Plailly/Science Photo Library. Reproduced with permission.
Paleontology: Paleontology, skeletons of Pachypleurosaurus, placodus, and mixosaurus, photograph. Hans & Cassidy. Courtesy of Gale Research.
Paleontology: Paleontology, skeleton of dinosaur preying on rat, illustration. Hans & Cassidy. Courtesy of Gale Research.
Paleontology: Paleontology, skeleton of small four-legged dinosaur, Jenkins, 1971. Hans & Cassidy. Courtesy of Gale Research.
Paleontology: Paleontology, illustration,skeleton of dinosaur with small wings, photograph. Hans & Cassidy. Courtesy of Gale Research.

Paleontology: Paleontology, three skeletons, photograph. Hans & Cassidy. Courtesy of Gale Research.
Paleontology: Paleontology, two illustrations, after Romer and Price, photograph. Hans & Cassidy. Courtesy of Gale Research.
Paleontology: Paleontology, after Chaline, photograph. Hans & Cassidy. Courtesy of Gale Research.
Paleontology: Paleontology, after Andrews, photograph. Hans & Cassidy. Courtesy of Gale Research.
Paleontology: Paleontology, after Moy, photograph. Hans & Cassidy. Courtesy of Gale Research.
Paleontology: Paleontology, after Gould, photograph. Hans & Cassidy. Courtesy of Gale Research.
Paleontology: Paleontology, parastylonurus, photograph. Hans & Cassidy. Courtesy of Gale Research.
Paleontology: Paleontology, illustration after Hupe, photograph. Hans & Cassidy. Courtesy of Gale Research.
Paleontology: Paleontology, after chaline, 1990, photograph. Hans & Cassidy. Courtesy of Gale Research.
Palms: Florida trees, photograph. JLM Visuals. Reproduced with permission.
Palms: Palms, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Panda: Panda, photograph. JLM Visuals. Reproduced with permission.
Pangaea: Pangaea, two oval shaped globes, illustration. Hans & Cassidy. Courtesy of Gale Research.
Pangolin: Small pangolin, photograph. © Jane Burton, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Paper: Paper mill, Georgia, photograph. © Ed Wheeler/Stock Market. Reproduced with permission.
Papin, Denis: Papin, Denis, portrait. The Library of Congress.
Parabola: Parabola, cone, illustration. Hans & Cassidy. Courtesy of Gale Research.
Parabola: Parabola, graph, photograph. Hans & Cassidy. Courtesy of Gale Research.
Parabola: Parabola, graph, illustration. Hans & Cassidy. Courtesy of Gale Research.
Parabola: Parabola, illustration. Hans & Cassidy. Courtesy of Gale Research.
Parachute: Splashdown, astropod splashing into sea, photograph. U. S. National Aeronautics and Space Administration (NASA).
Parallel: Parallel train tracks, photograph. © Sotographs/Stock Market. Reproduced with permission.
Parasites: Parasites, photograph. Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Pare, Ambroise: Pare, Ambroise, portrait. The Library of Congress.
Parrot: Parrot, photograph. Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Parrots: Parrots, photograph. Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Particle Accelerator: Electrostatic particle accelorator, photograph. © Philippe Plailly/Eurelios, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Particle detector: Electron in magnetic field spirals, photograph. © Lawrence Berkeley Laboratory/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Particle detectors: Particle detector, cerenkov radiation, photograph. Hans & Cassidy. Courtesy of Gale Research.
Particle detectors: Particle detector, ionizing particle, photograph. Hans & Cassidy. Courtesy of Gale Research.
Particle detectors: Particle detector, lucident radiation, photograph. Hans & Cassidy. Courtesy of Gale Research.
Particles, Subatomic: CLEO detector, electronic display, photograph. © Newman Laboratory of Nuclear Studies, Cornell University, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Partridges: Birds, Partidges, photograph. © David Stoeklein/Stock Market. Reproduced with permission.
Pascal, Blaise: Pascal, Blaise, photograph of painting. The Library of Congress.
Pauli, Wolfgang: Pauli, Wolfgang, photograph. The Library of Congress.
Pavlov, Ivan Petrovich: Pavlov, Ivan Petrovich, (standing), photograph. The Library of Congress.
Peafowl: Peafowl, photograph. Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Peccaries: Peccaries, photograph. Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Pelicans: Pelicans, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Penguin: Penguins, photograph. JLM Visuals. Reproduced with permission.
Penguins: King Penguins, photograph. JLM Visuals. Reproduced with permission.
Peninsula: Body of water, extending cliff, photograph. JLM Visual. Reproduced with permission.
Pepper: Red pepper plant, photograph. JLM Visuals. Reproduced with permission.
Perception: Perception, children, photograph. © Barbara Kirk/Stock Market. Reproduced with permission.
Perch: Redbreast sunfish, photograph. JLM Visuals. Reproduced with permission.
Peregrine falcon: Peregrine falcon, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Periodic functions: Periodic function, waves, illustration. Hans & Cassidy. Courtesy of Gale Research.
Periodic Functions: Periodic function, diagram, illustration. Hans & Cassidy. Courtesy of Gale Research.
Periodic functions: Periodic function figure, amplitude change, period change, phase shift, photograph. Hans & Cassidy. Courtesy of Gale Research.
Periodic table: Periodic table, illustration. Hans & Cassidy. Courtesy of Gale Research, Inc.
Periodic table: Periodic table, period 1-period 6, illustration. Hans & Cassidy. Courtesy of Gale Research.
Perkins, Jacob: Perkins, Jacob, portrait. The Library of Congress.
Perpendicular: Perpendicular, construction in process, photograph. © Vivian Moos/Stock Market. Reproduced with permissions.
Perpendicular: Perpendicular, ninety degree angle, photograph. Courtesy of Gale Research.
Perpendicular: Perpendicular, ninety-degree angles, photograph. Hans & Cassidy. Courtesy of Gale Research.
Perrin, Jean Baptiste Professor: Perrin, Jean Baptiste, photograph. The Library of Congress.
Perutz, Max: Perutz, Max, photograph. The Library of Congress.
Pesticides: Pesticides, illustration. Hans & Cassidy. Courtesy of Gale Research.
Pesticides: Pesticides, illustration. Hans & Cassidy. Courtesy of Gale Research.
Pests: Eight-spotted forester moth caterpillars, photograph. JLM Visuals. Reproduced with permission.
Petrels: Bird, Petrel, photograph. © CBC/Phototake. NYC. Reproduced with permission.
Petroglyphs and pictographs: Petroglyphs and pictographs, photograph. P. Carrara,U. S. Geological Survey.
Petroleum: Oil Pipeline, Alaska, photograph. JLM Visuals. Reproduced with permission.
pH: Chemistry, PH paper, photograph. © Yoav Levy/Phototake NYC Reproduced with permission.
Phases of matter: Calcium belted, hand, photograph. © Yoav Levy/Phototake NYC. Reproduced with permission.
Pheasants: Pheasants, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Pheasants: Pheasants, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Phenyl group: Phenyl group, Kekule resonance forms, photograph. Hans & Cassidy. Courtesy of Gale Research.
Philosophers, Authors, English: Bacon, Sir Francis, painting. The Library of Congress.
Phosphorus: Phosphorus, photograph. © Charles D. Winters, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Phosphorus removal: Phosphorus cycle, environment, photograph. Hans & Cassidy. Courtesy of Gale Research.
Photography: First known photograph, photograph. © The Bettman Archive. Reproduced with permission.
Photosynthesis: photosynthesis, zinnia leaf, photograph. © Dr. Jeremy Burgess/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Phototropism: Three potted plants, phototropism, photograph. © Nigel Cattlin, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Photovoltaic Cell: Desalineation system, phottovoltaic cell, photograph. © Mobil Solar Energy Corporation/Phototake NYC. Reproduced with permission.
Physical therapy: People in hydro-therapy pool, photograph. © Will & Deni McIntyre, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Physicists: Alvarez, Luis, (working on an experiment) photograph. The Library of Congress.
Physicists: Bohr, Niels, photograph. The Library of Congress.
Physicists: Fermi, Enrico, photograph. The Library of Congress.
Physicists: Lee, Tsung-Dao, photograph The Library of Congress.
Physicists: Szilard, Leo, photograph. The Library of Congress.
Physicists, Astrophysicists: Einstein, Albert, photograph. The Library of Congress.
Physicists, Scientists: Goeppert-Mayer, Maria, photograph. The Library of Congress.
Pig: Wild pig, photograph. JLM Visuals. Reproduced with permission.
Pigeons and Doves: Pigeons and doves, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Pigeons and doves: Pigeons and doves, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Pike: Pike, photograph. JLM Visuals. Reproduced with permission.
Pinecone Fish: Pinecone fish, photograph. JLM Visuals. Reproduced with permission.
Pines: Pines, photograph. James Lee Sikkema. Reproduced by permission.
Pines: Pines, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Pipefish: Pipefish, photograph. © Jen and Des Bartlett, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Piping plover: Piping plover, photgraph. © U.S. Fish & Wildlife Service.
Planck, Max: Planck, Max, photograph of sketch. The Library of Congress.
Planetary Atmospheres: Solar system formation, photograph. © David A. Hardy/ Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Planetary Nebulae: Cat's Eye Nebula, photograph. U.S. National Aeronautics and Space Administration (NASA).
Planetary nebulae: Planetary nebulae, photograph. U. S. National Aeronautics and Space Administration (NASA).
Planetary nebulae: Planetary nebulae in Aqaurius, photograph. U. S. National Aeronautics and Space Administration (NASA).
Planetary nebulae: Planetary Nebulae, X-ray image, photograph. U. S. National Aeronautics and Space Administration (NASA).
Planetary nebulae: Planetary nebulae, diagrams, photograph. Hans & Cassidy. Courtesy of Gale Research.
Planetary nebulae: Planetary nebulae, diagrams, transitions, photograph. Hans & Cassidy. Courtesy of Gale Research.
Planetary nebulae: Planetary nebulae, diagrams, photograph. Hans & Cassidy. Courtesy of Gale Research.
Planetary nebulae: Planetary Nebulae, two-photon emission, photograph. Hans & Cassidy. Courtesy of Gale Research.
Planetary ring systems: Neptune, Solar system, photograph. © NASA/Phototake NYC. Reproduced with permission.
Planetary ring systems: Saturn's rings, photograph. U. S. National Aeronautics and Space Administration (NASA).
Planetary ring systems: All known planetary rings, photograph. U. S. National Aeronautics and Space Administration (NASA).
Plant: Cross section of plant root, photograph. © Carolina Biological Supply Company/Phototake NYC. Reproduced with permission.
Plastic: Micrograph, biodegradable plastic, photograph. © National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Plastic: Plastic illustration. Robert L. Wolke. Reproduced with permission.
Plate Tectonics: Iceland, Rift Valley, Iceland, photograph. JLM Visuals. Reproduced with permission.
Plate Tectonics: San Andreas Fault, photograph. JLM Visuals. Reproduced with permission.
Plate tectonics: Plate tectonics, photograph. The Library of Congress.
Platinum: Platinum, photograph. © Russ Lappa/Science Source, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Plover: Plover bird, photograph. © Dr. M.F. Soper, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Plovers: Killdear, photograph. JLM Visuals. Reproduced with permission.
Pluto: Pluto, photograph. U. S. National Aeronautics and Space Administration (NASA).
Pluto: Pluto, orbit, surface markings, photograph. Hans & Cassidy. Courtesy of Gale Research.
Pluto: Pluto, illustration. Hans & Cassidy. Courtesy of Gale Research.
Pneumonia: X-Ray, ung, pnuemonia, photograph. © National Aududon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Poincari, Jules Henri Poincari, Jules Henri, portrait. The Library of Congress.
Point source: Point source, illustration. Hans & Cassidy. Courtesy of Gale Research.
Point source: Point source, illustration. Hans & Cassidy. Courtesy of Gale Research.
Polar coordinates: Polar coordinates, acute angle, photograph. Hans & Cassidy. Courtesy of Gale Research.
Polar coordinates: Polar coordinates, acute, obtuse angles, illustration. Hans & Cassidy. Courtesy of Gale Research.
Polar coordinates: Polar coordinates, acute angle, photograph. Hans & Cassidy. Courtesy of Gale Research.
Pollination: Bacteria, photograph. JLM Visuals. Reproduced with permission.
Pollination: Pollination, yellow flower and bee, photograph. © Zefa Germany 1994/Stock Market. Reproduced with permission.
Pollution: Cars on a freeway, portrait. The Library of Congress.
Pollution: Pollution, photograph. National Center for Atmospheric Research/University Corporation for Atmospheric Research/National Science Foundation 313. Reproduced with permission.
Pollution Control: Pollution control, photograph. © Tom Carrill/Phototake NYC. Reproduced with permission.
Polygons: Polygons, various shapes, photograph. Hans & Cassidy. Courtesy of Gale Research.
Polymer: Polymer, products, photograph. © Charles D. Winters, National Audubon Society Collecction/Photo Researchers, Inc. Reproduced with permission.
Polyurethane: Polyurethane foam, photograph. © Charles D. Winters, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Popov, Aleksandr Stepanovich: Popov, Aleksandr Stepanovich, portrait. The Library of Congress.
Poppies: Poppie flowers, photograph. JLM Visuals. Reproduced with permission.
Population , Human: Istanbul, Turkey, photograph. JLM Visuals. Reproduced with permission.
Porcupine: Porcupine, photograph. © Malcolm Boulton, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Potassium hydrogen tartrate: Potassium hydrogen tartrate, photograph. © Dr. Jeremy Burgess/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Powell, Cecil Frank: Powell, Cecil Frank, portrait. The Library of Congress.
Power plants: Power plant exterior, photograph. © Jeff Greenberg, The National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Power supply: Interior of power station, photograph. © James King-Holmes/Science Photo Library, The National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Prairie: Storm on prairie, Colorado Springs, photograph. © Myron Wood, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission
Prairie: Tall grass prairie, Montana, photograph. © Barry Griffiths, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Prairie Chicken: Bird, prairie chicken, photograph. JLM Visuals. Reproduced with permission.
Prairie dog: Prairie dog, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Praying mantis: Praying mantis, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Precession of the equinoxes: Precession of the equinox, globe, celestial sphere, photograph. Hans & Cassidy. Courtesy of Gale Research.

Precession of the equinoxes: Precession of the equinox, top spinning, photograph. Hans & Cassidy. Courtesy of Gale Research.
Precious metals: Precious metals, gold in quartz, photograph. © Otto Rogge/Stock Market. Reproduced with permission.
Precious metals: Precious metals, leaf gold, photograph. U. S. National Aeronautics and Space Administration (NASA).
Precipitation: Hailstones on grass, photograph. © Astrid & Hanns-Frieder Michler/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc.
Precipitation: Snow measuring, portrait. The Library of Congress.
Predator: Predators, cheetahs eating kill, photograph. © Stan Osolinski 1993/Stock Market. Reproduced with permission.
Prenatal surgery: Prenatal Surgery, three diagrams, photograph. Hans & Cassidy. Courtesy of Gale Research.
Prenatal surgery: Prenatal surgery, thyree diagrams of fetus, photograph. Hans & Cassidy. Courtesy of Gale Research.
Prescribed burn: Controlled burning of prairie, photograph. © Stephen J. Krasemann, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Presidents, Inventors: Jefferson, Thomas, photograph of painting. The Library of Congress
Presidents, World Leaders: Lincoln, Abraham, portrait. The Library of Congress.
Prey: Prey, photograph. © ED Cesar, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Priestley, Joseph: Priestley, Joseph, portrait. The Library of Congress.
Primates: Orangutan eating leaves, photograph. © Tom McHugh, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Primroses: Primroses, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Printing: Printing machines, photograph. © Tom Traoy/Stock Market. Reproduced with permission.
Probability theory: Probability theory, dice, photograph. © David Wood/Stock Market. Reproduced with permission.
Projective geometry: Projective geometry, illustration. Hans & Cassidy. Courtesy of Gale Research.
Projective geometry: Projective geometry, illustration. Hans & Cassidy. Courtesy of Gale Research.
Prokaryote: Prokaryote, blue-green alga, bacterial cell, photograph. Hans & Cassidy. Courtesy of Gale Research.
Pronghorn: Pronghorn, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Prosimians: Phillipine tarsier, photograph. © A. W. Ambler, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Prosthetics: Artificial knee joint, photograph. © Mike Devlin, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Prosthetics: Prosthetics, artificial leg, photograph. © Andrew Holbrooke/Stock Market. Reproduced with permission.
Prosthetics: Prosthetics, line drawing. Hans&Cassidy. Courtesy of Gale Research.
Prosthetics: Prosthetics, line drawing. Hans&Cassidy. Courtesy of Gale Research.
Prosthetics: Prosthetics, diagram of artifical limbs, photograph. Hans&Cassidy. Courtesy of Gale Research.
Protozoa: Protozoa, photograph. © Eric Grave/Science Source, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Proust, Joseph Louis: Proust, Joseph Louis, portrait. The Library of Congress.
Psychologists: Skinner, B.F., photograph The Library of Congress.
Psychometry: Psychometry, two women, photograph. © Will & Deni McIntyre, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Publishers, Authors: Franklin, Benjamin, photograph of painting. The Library of Congress.
Puffer: Fish, swellfish, photograph. © Jack Dermid, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Pulsar: Crab Nebula, images, photograph. U. S. National Aeronautics and Space Administration (NASA).
Purcell, Edward Mills: Purcell, Edward Mills, portrait. The Library of Congress.
Purkyne, Jan Evangelista: Purkyne, Jan Evangelista, portrait. The Library of Congress.
Purple Loosestrife: Purple loostrife, photograph. JLM Visuals. Reproduced with permission.
Pyramids: Pyramids at Giza, photograph. © Dilip Mehia/Contact Giza/Stock Market. Reproduced with permission.
Python: Green python, photograph. JLM Visuals. Reproduced with permission.
Quadrilateral: Quadrilateral, five different types, photograph. Hans & Cassidy. Courtesy of Gale Research.
Quadrilateral: Quadrilateral, crossing lines, photograph. Hans & Cassidy. Courtesy of Gale Research.
Quail: Quail, photograph. Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Quantum mechanics: Quantumm electrons, classical and quantum, photograph. Hans & Cassidy. Courtesy of Gale Research.
Quasar: Quasar, photograph. © Science Source, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Quasar: Quasar, photograph. U. S. National Aeronautics and Space Administration (NASA).
Rabi, I. I.: Rabi, I. I., portrait. The Library of Congress.
Rabies: Engraving, antirabies vaccination, Pasteur Inst., Paris, photograph. © Jean-Loup Charmet, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Raccoon: Racoon climbing tree, photograph. © Ron Sanford/Stock Market. Reproduced with permission.
Radar: View of Death Valley from Shuttle, photograph. © NASA/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Radar: Radar, line drawing. Hans & Cassidy. Courtesy of Gale Research.
Radial keratotomy: Radial keratotomy, scars, photograph. © Bob Masini/Phototake NYC. Reproduced with permission.
Radiation: Radiation, illustration. Robert L. Wolke. Reproduced with permission.
Radiation Detector: Geiger counter, radiation, photograph. © Hank Morgan, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Radiation exposure: Radiation exposure, photograph. U.S. National Aeronautics and Space Administration (NASA), courtesy of Greenpeace.
Radio: Radio towers, Az., photograph. © Tom Bean/Stock Market. Reproduced with permission.
Radio Astronomy: Satellite dishes, New Mexico. JLM Visuals. Reproduced with permission.
Radioactive tracers: Radioactive tracers, photograph. © CEA-Orsay/CNRI/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Radioactive tracers: Radioactive tracers, human body, photograph. Hans & Cassidy. Courtesy of Gale Research.
Radioactive waste: Radioactive waste, photograph. U. S. Department of Energy, Washington DC.
Radioactive waste: Radioactive waste, photograph. U. S. Department of Energy, Washington DC.
Radioactive waste management: Radioactive waste management, photograph. © Robert Visser, Greenpeace. Reproduced with permission.
Radioactive waste management: Radioactive waste management, photograph. U. S. Department of Energy, Washington DC.
Radioactivity: Pellet of plutonium, photograph. Science Source/ National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Radiology: Radiation treatment, photograph. © Martin Dohrn/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced by permission.
Rails: Rails, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Rainforest: Mountain rainforest, photograph. © Zefa Germany/Stock Market. Reproduced with permission.
Rainwater, James and Fitch, Val Logsdon: Rainwater, James and Fitch, Val Logsdon, portrait. The Library of Congress.
Raman, C. V.: Raman, C.V., photograph. The Library of Congress.
Ramey, Estelle R.: Ramey, Estelle R., portrait. The Library of Congress.
Ramon y Cajal, Santiago: Ramon y Cajal, Santiago, portrait. The Library of Congress.
Ramsay, William: Ramsay, William, portrait. The Library of Congress.
Ramsey, Norman Foster: Ramsey, Norman Foster, portrait. The Library of Congress.
Rangeland: Rangeland, photograph. © Thomas Braise Stock Market. Reproduced with permission.
Rat: Rat eating corn, photograph. © Leonard Lee Rue III, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Rays: Stingrays, photograph. © Norbert Wu/Stock Market. Reproduced with permission.
Reaction, Chemical: Combustion of sulfur, photograph. © Lawrence Migdale/Science Source/,National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Real numbers: Real numbers, line and triangle, illustration. Hans & Cassidy. Courtesy of Gale Research.
Rectangle: Rectangle figures, rectangle diagnol. altitude, illustration. Hans & Cassidy. Courtesy of Gale Research.
Recycling: Recycling, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Recycling: Recycling, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Red giant star: Red gaint star, circle, photograph. Hans & Cassidy. Courtesy of Gale Research.
Red giant star: Red giant star, graph, atomic weight vs. binding energy per baryon, photograph. Hans & Cassidy. Courtesy of Gale Research.

Red giant star: Red giant star. illustration, illustration. Hans & Cassidy. Courtesy of Gale Research.
Red giant star: Red giant star, flow chart, photograph.Hans & Cassidy. Courtesy of Gale Research.
Red Panda: Red panda, photograph. © S. Nagendra , National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission

Red Shift: Red giant star, black hole, photograph. © Julian Baum/ Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Redwoods: Redwoods, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission
Reflections: Three triangles with lines marked reflections, illustration. Hans & Cassidy. Courtesy of Gale Research.
Reflections: Reflections, graph, illustration. Hans & Cassidy. Courtesy of Gale Research.
Reflections: Reflections two triangles, photograph. Hans & Cassidy. Courtesy of Gale Research.
Reflections: Reflections, triangles, acute angle, photograph. Hans & Cassidy. Courtesy of Gale Research.
Reflections: Reflections, graph with line going through it horizontally, photograph. Hans & Cassidy. Courtesy of Gale Research.
Refrigeration: Industrial food refrigerator, photograph. © Stock Market. Reproduced with permission.
Relation: Relation, graph, line "X =Y", illustration. Hans & Cassidy. Courtesy of Gale Research.
Relation: Relation, graph with dotted line, photograph. Hans & Cassidy. Courtesy of Gale Research.
Rennie, John: Rennie, John, portrait. The Library of Congress.
Reproductive system: Reproductive system, female reproductive organs. © Bovari, John/ Custom Medical Stock Photo, Inc. Reproduced with permission.
Reptiles: Yellow-Headed collard lizard, photograph. © Rod Planck, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Resins: Raw polyethylene, photograph. © Chris Jones/Stock Market. Reproduced with permission.
Resonance: Resonance, two molecular structures, photograph. Hans & Cassidy. Courtesy of Gale Research.
Resonance: Resonance, "H" molecular structures, photograph. Hans & Cassidy. Courtesy of Gale Research.
Respirator: Respirator, photograph. © Ed Wheeler/Stock Market. Reproduced with permission.
Respiratory system: Respiratory system, diaphragm, photograph. Courtesy of Gale Research.
Retrograde motion: Retrograde motion, diagram, planets, stars, photograph. Hans & Cassidy. Courtesy of Gale Research.
Retrograde motion: Retrograde motion, people, trees, photograph. Hans & Cassidy. Courtesy of Gale Research.
Rh factor: Rh disease, flow chart demonstrating how Rh diasese is passed to fetus, illustration. Hans & Cassidy. Courtesy of Gale Research.

Rhesus Monkey: Rhesus Monkey, photograph. Charles H. Southwick. Reproduced with permission.
Rhinoceros: Rhinoceros, photograph. Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Rhinoceros: Rhinoceros, photograph. © U.S. Fish & Wildlife Service.
Ribonucleic acid (RNA): RNA, computer graphic, photograph. (c)Ken Eward/Science Source/ National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Ribonucleic acid (RNA): RNA, molecular structure, photograph. Hans & Cassidy. Courtesy of Gale Research.
Richards, Dickinson Woodruff Jr.: Richards, Dickinson Woodruff Jr., portrait. The Library of Congress.
Richards, Theodore William: Richards, Theodore William, portrait. The Library of Congress.
Richardson, Owen W.: Richardson, Owen W., portrait. The Library of Congress.
Richet, Charles Robert: Richet, Charles Robert, photograph. The Library of Congress.
Rickettsia: Rickettsia, photograph. © Alfred Pasteka/ASM/Science Source, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Rickover, Hyman G.: Rickover, Hyman G., portrait. The Library of Congress.
Ride, Sally: Ride, Sally, with crew members, photograph. U. S. National Aeronautics and Space Administration (NASA).
Rieman, Georg Friedrich Bernhard: Rieman, Georg Friedrich Bernhard, portrait. The Library of Congress.
River: Parana River, Brazil, photograph. © Carl Frank, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission

Robbins, Frederick: Robbins, Frederick, portrait. The Library of Congress.
Roberts, Lawrence: Roberts, Lawrence, portrait. The Library of Congress.
Robinson, Robert: Robinson, Robert, portrait. The Library of Congress.
Robotics: Police robot, live bomb, photograph. © Spencer Grant, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Rockets and Missiles: Arian rocket, European space agency, photograph. © David Parker, ESA/National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Rockets and missles: Rocket launching, missles,photograph. U. S. National Aeronautics and Space Administration (NASA).
Rocks: Triassic sandstone rocks, photograph. © John Buitenkant, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Rodents: Mole rat, photograph. © Tom McHugh, Photo Researchers, Inc. Reproduced with permission
Roemer, Olaus: Roemer, Olaus, portrait. The Library of Congress.
Root system: Root system, diagram, photograph. Hans & Cassidy. Courtesy of Gale Research.
Root system: Root system, emerging lateral roots, photograph. Hans & Cassidy. Courtesy of Gale Research.
Rose family: Rose, photograph. James Lee Sikkema. Reproduced by permission.
Rose family: Rose, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced by permission.
Rose family: Rose, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Ross, Ronald: Ross, Ronald, portrait. The Library of Congress.
Rotation: Rotation, two triangles, angle, photograph. Hans & Cassidy. Courtesy of Gale Research.
Rotation: Rotation, graph, photograph. Hans & Cassidy. Courtesy of Gale Research.
Rous, Peyton: Rous, Peyton, portrait. The Library of Congress.
Rubidium: Rubidium, photograph. © Russ Lappa/Science Source, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Ruffed Lermur: Lemur V. Variegatus, photograph. © Tom McHugh, National Audubon Society Collection/ Photo Researchers, Inc. Reproduced with permission
Rushes: Spike rush plant, photograph. JLM Visuals. Reproduced with permission.
Russell, Bertrand: Russell, Bertrand, (head and shoulders), photograph. The Library of Congress.
Rusts and smuts: Cedar-Apple rust on cedar tree, photograph. © Jim Zipp, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Rusts & Smuts: Smut on husked corn, photograph. © Leonard Lee Rue III, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Rutherford, Ernest: Rutherford, Ernest , photograph of sketch. The Library of Congress.
Sabin, Florence Rena: Sabin, Florence Rena,(head and shoulders), photograph of sketch. The Library of Congress.
Saiga Antelope: Saiga tatarica, photograph. © Akira Uchiyama, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Sakharov, Andrei: Sakharov, Andrei, photograph. The Library of Congress.
Salamander: Salamander, photograph. © Tom McHugh, National Audubon Society Collection/Photo Reseerchers, Inc. Reproduced with permission.

Salmon: Fish, salmon. © Kennan Ward/Stock Market. Reproduced with permissions.
Salt: Salt crystals, photograph. JLM Visuals. Reproduced with permission.
Saltwater : Salt formation Dead Sea, photograph. © Richard Nowitz/ Phototake NYC. Reproduced with permission.
Sand dollars: Keyhole sand dollar, photograph. JLM Visuals. Reproduced with permission.
Sandpipers and snipes: Sandpipers and snipes, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Sardines: Sardines, photograph. © Bill Longcore, National Audubon Society Collection/ Photo Researchers, Inc. Reproduced with permission.
Satellite: Intelsat VI satellite, photograph. © NASA, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Satellite: Satellite Echo I, photograph. U. S. National Aeronautics and Space Administration (NASA).
Satellite: Satellite, Astronaut attemptong to dock with solarmax, photograph. U. S. National Aeronautics and Space Administration (NASA).
Saturn: Saturn without rings, photograph. NASA. Reproduced with permission.
Saturn: Saturn with its rings, photograph. NASA. Reproduced with permission.
Saturn: Saturn's moon, Dione, photograph.U. S. National Aeronautics and Space Administration (NASA).
Saturn: Saturn, diagram, photograph. Hans & Cassidy. Courtesy of Gale Research.
Savannas: Zebra, photograph. JLM Visuals. Reproduced with permission.
Saxifrage family: Saxifrage tree, photograph. JLM Visuals.Reproduced with permission.
Scanning Tunneling Microscope: Silicon, scanning tunneling microscope, photograph. © Account Phototake /Phototake NYC Reproduced with permission.

Scavenger: Vultures , giraffe , photograph. JLM Visuals. Reproduced with permission.
Scheele, Carl Wilhelm: Scheele, Carl Wilhelm, portrait. The Library of Congress.
Schematic of present-day solar system: Schematic of present-day solar system, obit dregee markings of planets, photograph. Hans & Cassidy. Courtesy of Gale REsearch.
Schistosomiasis: Schistosomiasis, male and female, photograph. © Goivaux Communication/Phototake NYC Reproduced with permission.
Schleiden, Matthias Jacob: Schleiden, Matthias Jacob, portrait. The Library of Congress.
Schobein, Christian: Schobein, Christian, portrait. The Library of Congress.
Schrodinger, Erwin: Schrodinger, Erwin, photograph of sketch. The Library of Congress.
Schwann, Theodor Ambrose: Schwann, Theodor Ambrose, portrait. The Library of Congress.
Schwinger, Julian: Schwinger, Julian, photograph. The Library of Congress.
Scientists: Bush, Vannevar, photograph. The Library of Congress.
Scientists: Franck, James, photograph. The Library of Congress.
Scientists: Jacob, Francois, photograph. The Library of Congress.
Scientists: Joliet-Curie, Irene, photograph. The Library of Congress.
Scientists: Nobel, Alfred, photograph. The Library of Congress.
Scientists: Oppenheimer, J. Robert, photograph. The Library of Congress.
Scientists: Pasteur, Louis, photograph. The Library of Congress.
Scientists: Pauling, Linus, photograph. The Library of Congress.
Scientists: Urey, Harold, photograph. The Library of Congress.
Scientists: von Braun, Wernher, photograph. The Library of Congress.
Scientists: Wiener, Norbert, photograph. The Library of Congress.
Scientists: Bethe, Hans (Dr.), photograph. AP/Wide World Photos. Reproduced by permission.
Scorpionfish: Lion fish, coral sea, photograph. JLM Visuals. Reproduced with permission.
Sculpins: Sculpins, photograph. JLM Visuals. Reproduced with permission.
Sea anemone: Sea Anemone, photograph. JLM Visuals. Reproduced with permission.
Sea Cucumbers: Sea Cucumbers, photograph. JLM Visuals. Reproduced with permission.
Sea level: Hilly region, sea level view, photograph. JLM Visuals. Reproduced with permission.
Sea Lion: Sea Lions, photograph. Jen and Des Bartlett, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Sea squirts and salps: Sea-peach tunicate, photograph. JLM Visuals. Reproduced with permission.
Sea urchins: Sea Urchin, photograph. JLM Visuals. Reproduced with permission.
Seaborg, Glenn T.: Seaborg, Glenn T., photograph. The Library of Congress.
Seahorse: Spotted seahorse, photograph. © Jen and Des Bartlett, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Seal: Fur seal bull, photograph. © Leonard Lee Rue III, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Seals: Seals, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Seasons: Winter, Pocono Mountains, Pennsylvania, photograph. © Michael P. Gedomski, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Seasons: Seasons, Pocono Mountains, Pennsylvania, photograph. © Michael P. Gedomski, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Seasons: Seasons, Pocono Mountains, Pennsylvania, photograph. © Michael P. Gedomski, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Seasons: Fall, Pocono Mountains, Pennsylvania, photograph. © Michael P. Gedomski, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Seasons: Seasons, obit, photograph. Hans & Cassidy. Courtesy of Gale Research.
Secretary Bird: Secretary bird, photograph. © Jen and Des Bartlett, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Sedges: Cotton field, photograph. JLM Visuals. Reproduced with permission.
Sedges: Brooks Rouge, Alaska, photograph. JLM Visuals. Reproduced with permission.
Sediment and sedimentation: Sediment, gravel pit, photograph. JLM Visuals. Reproduced with permission.
Sediment and sedimentation: Sediment and sedimentation, grain size, velocity, photograph. Hans & Cassidy. Courtesy of Gale Research.
Sediment and sedimentation: Sediments and sedimentation, chart, photograph. Hans & Cassidy. Courtesy of Gale Research.
Sedimentary rock: Stockbridge marble, limestone, photograph. © A. W. Ambler, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Seed: Grass seeds, photograph. © Roy Morsch/Stock Market. Reproduced with permission.
Segmented Worms: Segmented worm, photograph. JLM Visuals. Reproduced with permission.
Segmented Worms: Leech, segmented worms, photograph. JLM Visuals. Reproduced with permission.
Segre, Emilio G.: Segre, Emilio G., portrait. The Library of Congress.
Seismograph: Seismograph, photograph. © Yoav Levy/Phototake NYC Reproduced with permission.
Seitz, Frederick: Seitz, Frederick, portrait. The Library of Congress.
Selenium: Dish of selenium, photograph. © Rich Treptow, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Semenov, Nikolai: Semenov, Nikolai, portrait. The Library of Congress.
Semmelweis, Ignaz Philipp: Semmelweis, Ignaz Philipp, portrait. The Library of Congress.
Sequoia: Sequoia tree, General Sherman tree, photograph. JLM Visuals. Reproduced with permission.
Set theory: Set theory, illustration, photograph. Hans & Cassidy. Courtesy of Gale Research.
Set theory: Set theory figure, photograph. Hans & Cassidy. Courtesy of Gale Research.
Set theory: Set theory figure, union, photograph. Hans & Cassidy. Courtesy of Gale Research.
Set theory: Set theory figure, intersection, photograph. Hans & Cassidy. Courtesy of Gale Research.
Set theory: Set theory, difference, photograph. Hans & Cassidy. Courtesy of Gale Research.
SETI - extraterrestrial life: SETI - extraterrestrial life, photograph. SETI Institute/Science Photo Library, National Audubon Society/Photo Researchers, Inc. Reproduced by permission.
Sewage Treatment: Sewage treatment, photograph. © Andrea Brizzi/Stock Market. Reproduced with permission.
Sewing machine: Sewing maching, photograph. © Gabe Palmer, The Stock Market. Reproduced with permission.
Sextant: Sextent, star navigation, photograph. © Gabe Palmer/Bikderberg/Stock Market. Reproduced with permission.
Sexually transmitted diseases: Sexually transmitted disease, flow chart, photograph. Hans & Cassidy. Courtesy of Gale Research.
Sexually transmitted diseases (STD): Syphilitic infection, sexually transmitted disease, photograph. © CNRI/Phototake NYC Reproduced with permission.
Shapley, Harlow: Shapley, Harlow, photograph. The Library of Congress.
Shark: Killer shark, photograph. © G. Carleton Ray, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Sheep: Sheep, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Sheep: Sheep grazing on field, photograph. © Richard Dibon-Smith, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Sherrington, Charles Scott: Sherrington, Charles Scott, photograph of sketch. The Library of Congress.
Shockley, William: Shockley, William, photograph. The Library of Congress.
Shore birds: Shore birds, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Shrew: Common, masked shrew, tree trunk, photograph. © Leonard Lee Rue, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Shrike: Great Northern shrike, photograph. © Hugh M. Halliday, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Shrimp: Shrimp, water, photograph. JLM Visuals. Reproduced with permission.
Siamang: Siamang yelling from tree, photograph. © R. Van Nosstrand, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Sickle cell anemia: Micrograph, red blood cells, sickle cell, photograph. © Dr. Gopal Murti, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Siegbahn, Karl M.G.: Siegbahn, Karl M.G., portrait. The Library of Congress.
Silicon: Silicon bar, photograph. © Charles D. Winters, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Silk cottons family: Baobab tree, photograph. JLM Visuals. Reproduced with permission.
Silver: Silver, photograph. © Bryan Peterson/Stock Market. Reproduced with permission.
Similarity: Similarity, traingles, photograph. Hans & Cassidy. Courtesy of Gale Research.
Similarity: Similarity, height, tree, pencil, illustration. Hans & Cassidy. Courtesy of Gale Research.
Similarity: Similarity, triangle, photograph. Hans & Cassidy. Courtesy of Gale Research.
Similarity: Similarity, recatngles, illustration. Hans & Cassidy. Courtesy of Gale Research.
Simple Machine: Technology, stone being pulled up, photograph. © Yoav Levy/Phototake NYC. Reproduced with permission.
Sinilarity: Similarity, triangle facing left, illustration. Hans & Cassidy. Courtesy of Gale Research.
Skate: Big skate, raja binoculata, photograph. © Tom McHugh, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Skeletal system: Human skeleton, frontal view, photograph. © Martin Dohrn, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Skeletal system: Micrograph of spongy bone, photograph. © Prof. P. Motta/Department of Anatomy/University "La Sapienza", Rome/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Skink: Skink, rocks, photograph. JLM Visuals. Reproduced with permission.
Skunk: Striped skunk, photograph. JLM Visuals. Reproduced with permission.
Skyscrapers: Buildings, skyscrapers, photograph. © Frank Shorty Wilcox/Stock Market. Reproduced with permission.
Slash and Burn: Slash and burn of field, photograph. © Marco Polo/Phototake NYC. Reproduced with permission.
Slash and Burn: Slash and burn of a forest, photograph. © Asa C. Thoresen, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Sleep disorders: Man in hospital bed, sleeping disorder, photograph. © Russell D. Curtis, National Audubon Society Collection/ Photo Researchers, Inc. Reproduced with permission.
Sloth: Sloth hanging from tree, photograph. © James R. Simon, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Slugs: Banana slug, photograph. JLM Visuals. Reproduced with permission.
Smallpox: Small pox, man's arm, photograph. © C. James Webb/Phototake NYC. Reproduced with permission.
Smell: Smell, illustration of human smell, photograph. Hans & Cassidy. Courtesy of Gale Research.
Smog: Smog over city, photograph. © Vivian Moos/Stock Market. Reproduced with permission.
Snail: Snail, photograph. JLM Visuals. Reproduced with permission.
Snake: Snakes, photograph. Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Snakes: Snakes, photograph. Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Snapdragon family: Snapdragon, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Snell, Willbrord: Snell, Willbrord, photograph. © Science Photo Library, National Audubon Society/Photo Researchers, Inc. Reproduced by permission.

Soap: Soap, photograph. Robert L. Wolke. Reproduced with permission.
Sociologists: Kinsey, Alfred, photograph. The Library of Congress.
Soddy, Frederick: Soddy, Frederick, portrait. The Library of Congress.
Sodium: Sodium stored in oil, photograph. © Lawrence Migdale/Science Source, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Sodium benzoate: Sodium benzoate, molecular structure, photograph. Hans & Cassidy. Courtesy of Gale Research.
Sodium benzoate: Sodium benzoate, molecular structure, photograph. Hans & Cassidy. Courtesy of Gale Research.
Sodium benzoate: Sodium benzoate, benzoic acid, photograph. Hans & Cassidy. Courtesy of Gale Research.
Sodium chloride: Sodium chloride, photograph. JLM Visuals. Reproduced with permission.
Sodium hydroxide: Sodium hydroxide crystals, photograph. © Charles D. Winter, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Soil: Soil profile with chalk rock, photograph. © Joyce Photographics, National Audubon Society Collection /Photo Researchers, Inc. Reproduced with permission.
Solar activity cycle: Solar activity, false coulour image of sun, photograph. (c)NASA/JISAS/ Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Solar activity cycle: Solar activity, three graphs, illustration. Hans & Cassidy. Courtesy of Gale Research.
Solar breeder: Solar panels, portrait. The Library of Congress.
Solar Energy Research, Development and Demonstration Act: Solar Energy Research, Development and Demonstration Act, photograph. U. S. Department of Energy, Washington DC.
Solar Flare: Solar flare, photograph. U. S. National Aeronautics and Space Administration (NASA).
Solar system Solar system, diagram, photograph. NASA. Reproduced with permission.
Solar system: Solar system, diagram, photograph. Hans & Cassidy. Courtesy of Gale Research.
Solar system: Solar system, illustration. Hans & Cassidy. Courtesy of Gale Research.
Solar system: Solar system, graph, temperature vs. distance from sun, photograph. Hans & Cassidy. Courtesy of Gale Research.
Solar System: Solar system, daigram, degree markings of planets, photograph. Hans & Cassidy. Courtesy of Gale Research.
Solar system: Solar system, photograph. © John Foster/Science Photo Library, National Audubon Society/Photo Researchers, Inc. Reproduced by permission.
Solar wind: Sun in magnetic I, photograph. U. S. National Aeronautics and Space Administration (NASA).
Solar wind: Solar wind, photograph. U. S. National Aeronautics and Space Administration (NASA).
Solubility: Solubility, graph, temperature vs. solubility, illustration. Hans & Cassidy. Courtesy of Gale Research.
Solution: Solution, illustration. Robert L. Wolke. Reproduced with permission.
South America: Map of South America, photograph. © Hammond Inc./ Phototake NYC Reproduced with permission.
South America: South America, illustration. Hans & Cassidy. Courtesy of Gale Research.
South America: South America, map, photograph. Hans & Cassidy. Courtesy of Gale Research.
Southwest Asian garden dormouse: Garden dormouse, photograph. © Tom McHugh, Photo Researchers, Inc. Reproduced with permission
Space Probe: Mariner 10, space probe, photograph. U. S. National Aeronautics and Space Administration (NASA).
Space probe: Space probe, diagram, earth, photograph. Hans & Cassidy. Courtesy of Gale Research.
Space probe: Space probe, gravitational pull, photograph. Hans & Cassidy. Courtesy of Gale Research.
Space Shuttle: Space shuttle, photograph. U. S. National Aeronautics and Space Administration (NASA).
Space shuttle: The Orbiter, Columbia, photograph. U. S. National Aeronautics and Space Administration (NASA).
Space shuttle: Space shuttle Atlantis,photograph. U. S. National Aeronautics and Space Administration (NASA).
Space shuttle: Satellite view of space shuttle challanger, photograph. U. S. National Aeronautics and Space Administration (NASA).
Space Station: Salyut space station, photograph. © Novosti Press Agency, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Spacecraft, manned: Manned spacecraft, photograph. U. S. National Aeronautics and Space Administration (NASA).
Spacecraft, manned: Gemini 3, 1965, photograph. U. S. National Aeronautics and Space Administration (NASA).
Spacecraft Voyager: Spacecraft voyager, photograph. U. S. National Aeronautics and Space Administration.
Spark plug: Spark plug, line drawing. Hans & Cassidy. Courtesy of Gale Research.
Spark plug: Spark plug, line drawing. Hans & Cassidy. Courtesy of Gale Research.
Spark plug: Spark Plug, diagram, photograph. Hans & Cassidy. Courtesy of Gale Research.
Sparrows and Bunting: Sparrows and buntings, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Sparrows and buntings: Sparrows and buntings, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Species: Earless lizards, photograph. JLM Visuals. Reproduced with permission.
Spectroscope: Spectroscope, diagram, photograph. Hans & Cassidy. Courtesy of Gale Research.
Spectroscopy: Electron spectroscopy, chemical analysis, photograph. © Joseph Nettis, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Spectrum: Spectrum, graph, wavelength vs. radiant power, photograph. Hans & Cassidy. Courtesy of Gale Research.
Spectrum: Spectrum, light shining through spectrum, rainbow, photograph. Hans & Cassidy. Courtesy of Gale Research.
Spectrum: Spectrum, bar graph, illustration. Hans & Cassidy. Courtesy of Gale Research.
Sperry, Roger Wolcott: Sperry, Roger Wolcott, photograph. The Library of Congress.
Spider Monkey: Spider monkey, tree, photograph. © S. Nagendra, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Spiderwart family: Spiderwart plants, photograph. JLM Visuals. Reproduced with permission.
Spina Biffida: Spina Biffida, small baby, photograph. © Biophoto Associates, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Spiny Anteater: Echidna, photograph. © Jen and Des Bartlett, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Spiral: Loretto chapel spiral staircase, photograph. © G. R. Gainer/Stock Market. Reproduced with permissions.
Spirometer: Spirometer, man breathing, photograph. Hans & Cassidy. Courtesy of Gale Research.
Spirometer: Spirometer, illustration. Hans & Cassidy. Courtesy of Gale Research.
Sponge: Vase sponge, photograph. © Nancy Sefton, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Spore: Polypody fern leaf, photograph. © Hugh Spencer, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Spruce family: Spruce family, photograph. James Lee Sikkema. Reproduced by permission.
Spurge family: Spurge family, photograph. James Lee Sikkema. Reproduced by permission.
Spurge Family: Rubber tree, Fiscus Elastica, photograph. JLM Visuals. Reproduced with permission.
Squid: Common squid, photograph. © Omikron, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Squirrel Fish: Orange squirrel fish, photograph. © Stephen Frink/Stock Market. Reproduced with permissions.
Squirrels: Squirrels, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
St. Vincent parrot: St. Vincent Parrot, photograph. © Tom McHugh , National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Stanley, Wendell Meredith: Stanley, Wendell Meredith, photograph. The Library of Congress.
Star: Antares star, photograph. © Ronald Royer/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Star: Star, arrows pointing towards center, photograph. Hans & Cassidy. Courtesy of Gale Research.
Star: Graph, light curve, photograph. Hans & Cassidy. Courtesy of Gale Research.
Star: Star, graph, magnitude vs. hours, photograph. Hans & Cassidy. Courtesy of Gale Research.
Star: Star, earth, center, human, photograph. Hans & Cassidy. Courtesy of Gale Research.
Star cluster: Pleiades, photograph. © Royal Observatory, Edinburgh/AATB/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Star Formation: Starbirth, photograph. © Dr. Ian Gatley/Science Photo Library. Reproduced with permission.
Starfish: Starfish, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Stark, Johannes: Stark, Johannes, portrait. The Library of Congress.
Starlings: Flocks of starlings, photograph. © Joe Munroe, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Starlings: Golden breast starlings, photograph. © Michele Burgess/Stock Market. Reproduced with permission.
States of matter: SEAgel, photograph. © Lawrence Livermore National Laboratory/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
States of matter: States of matter, illustration. Robert L. Wolke. Reproduced with permission.
States of matter: States of matter, illustration. Robert L. Wolke. Reproduced with permission.
States of Matter: Dry ice subliming, photograph. © Charles D. Winters, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Staudinger, Hermann: Staudinger, Hermann, portrait. The Library of Congress.
Stealth technology: Stealth bombers, photograph. The Library of Congress.
Steam engine: Steam engine, photograph. © Mark Gamba/Stock Market. Reproduced with permission.
Steam Pressure Sterilizer: Steam pressure sterilizer, woman, illustration. Hans & Cassidy. Courtesy of Gale Research.
Stearic acid: Stearic Acid, molecular structure, glycerol, stearic acid, triacyl glycerol, water, photograph. Hans & Cassidy. Courtesy of Gale Research.
Stearic Acid: Stearic Acid, ,molecular structure of phospholipid, illustration. Hans & Cassidy. Courtesy of Gale Research.
Stearic acid: Stearic Acid, molecular structure, glyclolipid, water, stearic acid, glycerol, photograph. Hans & Cassidy. Courtesy of Gale Research.
Stellar Evolution: Steller evolution, main stages, photograph. © David A. Hardy / Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Stereochemistry: Stereochemistry, methane, illustration. Hans & Cassidy. Courtesy of Gale Research.
Stereochemistry: Stereochemistry, formaldehyde, photograph. Hans & Cassidy. Courtesy of Gale Research.
Stereochemistry: Stereochemistry, dichloroethene, illustration. Hans & Cassidy. Courtesy of Gale Research.
Stereochemistry: Stereochemistry, carvone, photograph. Hans & Cassidy. Courtesy of Gale Research.
Stereochemistry: Stereochemistry, antibacterial, inactive, photograph. Hans & Cassidy. Courtesy of Gale Research.
Stern, Otto: Stern, Otto, portrait. Courtesy of The Library of Congress
Stethoscope: Stethoscope, line drawing. Hans & Cassidy. Courtesy of Gale Research.
Stethoscope: Stethoscope, line drawing. Hans & Cassidy. Courtesy of Gale Research.
Stethoscope: Stethoscope, diagram of stethoscope, photograph. Hans&Cassidy. Courtesy of Gale Research.
Stilts and avocets: Stilt bird, eggs, photograph. © Eric Hosking, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Stomatolites: Stromatelites, Hanelin Pool, Western Australia, photograph. © Francois Gohier, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Stone and masonry: Marble quarry, Carrara, Italy, photograph. © Sheila Terry/Science Photo Library, The National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Stork: Stork, photograph. JLM Visuals. Reproduced with permission.
Storks: Storks, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Storm: Storm, photograph. © National Center for Atmospheric Research/University Corporation for Atmospheric Research/National Science Foundation 1150. Reproduced with permission.
Storm: Storm, photograph. © National Center for Atmospheric Research/University Corporation for Atmospheric Research/National Science Foundation 1150. Reproduced with permission.
Storm: Storm, photograph. National Oceanic and Atmospheric Administration.
Strata: Strata, photograph. © M. Woodbridge Williams, National Park Service. Reproduced with permission.
Strip mining: Coal strip mining in Pennsylvania, photograph. © Francois Gohier, The National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Stroke: Stroke, diagram of brain, photograph. Hans & Cassidy. Courtesy of Gale Research.
Stromatolite: Stromatolite, photograph. © P. Carrara, U. S. Geological Survey Photographic Library Denver, CO.
Sturgeon: Lake Sturgeon, photograph. © Tom McHugh, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Subatomic Particles: Cloud chamber, photograph. © Lawrence Berkeley, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Subatomic particles: Subatomic particles, line drawing. Hans & Cassidy. Courtesy of Gale Research.
Submarine: General Dynamics trident submarine, photograph. © Tom Kelly/Phototake NYC. Reproduced with permission.
Subsidence: Subsidence, photograph. © C. R. Dunrud/U. S. Geological Survey Photographic Library Denver, CO.
Succession: Old field succession, photograph. © John Dudak/Phototake NYC Reproduced with permission.
Sulfur: Piece of sulfur, photograph. JLM Visuals. Reproduced with permission.
Sulfur cycle: Sulfur cycle, environment, photograph. Hans & Cassidy. Courtesy of Gale Research.
Sulfuric acid: Acid dehydration of sugar, photograph. © David Taylor/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Sumner, James B.: Sumner, James B., portrait. The Library of Congress.
Sun: Sun, photograph. U. S. National Aeronautics and Space Administration (NASA).
Sun: Sun from skylab, solar flare, photograph. U. S. National Aeronautics and Space Administration (NASA).
Sunspots: Sunspots, visible light images, photograph. U.S. National Aeronaitics and Space Administration (NASA).
Superconductivity: Superconductivity, graph, temperature, magnetic field, photograph. Hans & Cassidy. Courtesy of Gale Research.
Superconductor: Meissner effect, superconductor., photograph. © Yoav Levy/Phototake NYC. Reproduced with permission.
Superconductor: Superconductor, graph, R vs T, photograph. Hans & Cassidy. Courtesy of Gale Research.
Superconductor: Superconductor, meissner state, mixed state, normal state, illustration. Hans & Cassidy. Courtesy of Gale Research.
Superconductor: Superconductor, graph year of disc. vs. Tc, photograph. Hans & Cassidy. Courtesy of Gale Research.
Superconductor: Superconductor, two circles, photograph. Hans & Cassidy. Courtesy of Gale Research.
Superconductor: Superconductor, crystal surface, photograph.Courtesy of Gale Research.
Superconductor: Superconductor, diagram, photograph. Hans & Cassidy. Courtesy of Gale Research.
Supernova: Blast fro, photograph. U. S. National Aeronautics and Space Administration (NASA).
Supernova: Supernova, Cassiopeia, photograph. U. S. National Aeronautics and Space Administration (NASA).
Surface of Mars: Surface of Mars, photograph. U. S. National Aeronautics and Space Administration.
Surface tension: Waterstrider bug, photograph. © Hermann Eisenbeiss, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Surgery: Neurosurgeon, robot arm, photograph. © Geoff Tompkincon, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Svedberg,Theodor: Svedberg, Theodor, portrait. The Library of Congress.
Swallows and Martins: Swallows and martins, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Swamp cypress family: Swamp cypress, photograph. James Lee Sikkema. Reproduced by permission.
Swamp cypress family: Cypress tree, forest, photograph. JLM Visuals. Reproduced with permission.
Swans: Swans, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Swifts: Swift holding on to brick wall. © Duryea Morton, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Symbiosis: Cape buffalo, photograph. JLM Visuals. Reproduced with permission.
Synge, Richard L.M.: Synge, Richard L.M., portrait. The Library of Congress.
Synthesizer, voice: Computers, voice synthesizer, photograph. © Srulik Haramaty/Phototake NYC. Reproduced with permission.
Tamm, Igor: Tamm, Igor, portrait. The Library of Congress.

Tanagers: Tanagers, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Tapirs: Tapirs, photograph. © Planet Earth. Reproduced with permission.
Tarsier: Mindanao tarsier, photograph. © Omikron, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Tartaglia, Niccolo Fontana: Tartaglia, Niccolo Fontana, portrait. The Library of Congress.
Tartaric acid: Tartaric acid, molecular structures, illustration. Hans & Cassidy. Courtesy of Gale Research.
Tasmanian Devil: Tasmanian devil, photograph. JLM Visuals. Reproduced with permission.
Taste: Taste, diagram of taste buds,photograph. Hans & Cassidy. Courtesy of Gale Research.
Taube, Henry: Taube, Henry, portrait. The Library of Congress.
Taylor, Frederick Winslow: Taylor, Frederick Winslow, photograph of sketch. The Library of Congress.
Tea plant: Tea plants, photograph. JLM Visuals. Reproduced with permission.
Tectonics: Tectonics, photograph. © W. R. Normark/U. S. Geological Survey Photographic Library Denver, CO.
Telephone: Telephone, diagram, illustration. Hans & Cassidy. Courtesy of Gale Research.
Telephone: Telephone, diagram, office system, photograph. Hans & Cassidy. Courtesy of Gale Research.
Telephone: Telephone, conventional telephone central office, photograph. Hans & Cassidy. Courtesy of Gale Research.
Telescope: Anglo-Australian telescope, photograph. © Royal Observatory, Edinburgh/National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Telescope: Telescope,photograph. © Roger Ressmeyer/Starlight/for the W. M. Keck Observatory, courtesy of California Associate for Research and Astronomy.
Telescope: Telescope, lines, photograph. Hans & Cassidy. Courtesy of Gale Research.
Telescope: Telescope, four kinds, photograph. Hans & Cassidy. Courtesy of Gale Research.
Telescope: Telescope, diagram, photograph. Hans & Cassidy. Courtesy of Gale Research.
Television: Woman, two leopards, photograph. © Philippe Plailly/Science Photo Library, The National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Teller, Edward: Teller, Edward, photograph. The Library of Congress.
Tellurium: Tellurium, photograph. © Russ Lappa/Science Source, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Temperature Regulation: Canines, North American Timber Wolf, photograph. © Frank Rossotto/Stock Market. Reproduced with permission.
Tenrecs: Tenrec, photograph. © Howard E. Uible, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Terns: Terns, photograph. Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Terracing: Rice terraces, Bali, photograph. JLM Visuals. Reproduced with permission.
Territoriality: Walruses, photograph. JLM Visuals. Reproduced with permission.
Tesla, Nikola: Tesla, Nikola, portrait. The Library of Congress.
Texas blind salamander: Texas blind salamander, photograph. © U.S. Fish & Wildlife Service.
Textiles: Computerized textile mill, photograph. © Mark Antman/Phototake NYC. Reproduced with permission.
Theorell, Alex H.T.: Theorell, Alex H.T., portrait. The Library of Congress.
Thermal expansion: Bridge expansion joint, photograph. JLM Visuals. Reproduced with permission.
Thermal expansion: Thermal expansion, fish, ice, photograph. Hans & Cassidy. Courtesy of Gale Research.
Thermal expansion: Thermal exoansion, iron and aluminum, photograph. Hans & Cassidy. Courtesy of Gale Research.
Thermal expansion: Thermal expansion, thermometers, photograph. Hans & Cassidy. Courtesy of Gale Research.
Thermometer: Digital thermometer, photograph. © Adam Hart-Davis, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Thistle: Thistle, photograph. Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Thistle: Thistle, photograph. Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Thompson, Benjamin: Thompson, Benjamin , portrait. The Library of Congress.
Thomson, J. J.: Thomson, J. J., photograph of sketch. The Library of Congress.
Thomson, William: Thomson, William , portrait. The Library of Congress.
Three Mile Island: Three Mile Island, photograph. Robert Visser, Greenpeace Reproduced with permission.
Thrombosis: Electron micrograph of thrombus, photograph. © Moredun Animal Health LTD, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Thrushes: Thrushes, photograph. Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Thrushes: Thrushes, photograph. Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Thunderstorm: Lightning, photograph. © Kent Wood, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Thunderstorm: Thunderstorm, photograph. National Center for Atmospheric Research/University Corporation for Atmospheric Research/National Science Foundation 466. Reproduced with permission.
Thunderstorm: Thunderstorm, depiction of precipitation. National Oceanic and Atmospheric Administration.
Tides: Tides, photograph. JLM Visuals. Reproduced with permission.
Tides: Tides, photograph. JLM Visuals. Reproduced with permission.
Tiger: Tiger, photograph. Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Time: Clock, Scott'y castle, photograph. JLM Visuals. Reproduced with permission.
Times Beach, MO: Times Beach, MO, photograph. © Sam Kittner, Greenpeace. Reproduced with permission.
Tin: Tin, photograph. © Russ Lappa, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Tit family: Tit family, photograph. Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Titanium: Titanium products, photograph. © Account Phototake/Phototake NYC. Reproduced with permission.
Toad: Toad, photograph. © U.S. Fish & Wildlife Service.
Tonsillitis: Tonsillitis, diagram of tonsils, illustration. Hans & Cassidy. Courtesy of Gale Research.
Topology: Topology, loop, illustration. Hans & Cassidy. Courtesy of Gale Research.
Topology: Topology, twp circles next to eachother, triangle, photograph. Hans & Cassidy. Courtesy of Gale Research.
Topology: Topology, circle, oval, photograph. Hans & Cassidy. Courtesy of Gale Research.
Topology: Topology, two shapes with five sides, photograph. Hans & Cassidy. Courtesy of Gale Research.
Topology: Topology, snake-like shape, photograph. Hans & Cassidy. Courtesy of Gale Research.
Tornados: Tornado funnel cloud, photograph. © Photri/Bikderberg/Stock Market. Reproduced by permissions.
Toucan: Bird, toucan, photograph. © Roy Morsch/Stock Market. Reproduced with permission.
Touraco: Touraco, tree, photograph. © Kenneth W. Fink, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Toxic Substance: Toxic substance, photograph. © Lorette Dorreboom, Greenpeace. Reproduced with permission.
Trains and Railroads: Train, photograph. JLM Visuals. Reproduced with permission.
Transducers: Assortment of transducers, photograph. © Levy Yoav/Phototake NYC. Reproduced with permission.
Transformer: High voltage transformer, photograph. © Tardos Camesi/Bikderberg/Stock Market. Reproduced with permissions.
Transistor: Section of transistor, photograph. © Michael Abbey/Science Source, The National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Transistor: Transistor , portrait. The Library of Congress.
Translations: Translations, two triangles, photograph. Hans & Cassidy. Courtesy of Gale Research.
Translations: Translations, three triangles, illustration. Hans & Cassidy. Courtesy of Gale Research.
Translations: Translations, right angles, equation, photograph. Hans & Cassidy. Courtesy of Gale Research.
Transpiration: Transpiration, photograph. © National Center for Atmospheric Research/University Corporation for Atmospheric Research/National Science Foundation 1018.
Transplant, surgical: Dylan Stork, heart transplant, photograph. © Alexander Tsiaras, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Trapezoid: Trapezoid, photograph. Hans & Cassidy. Courtesy of Gale Research.
Trapezoid: Trapezoid, shape, illustration. Hans & Cassidy. Courtesy of Gale Research.
Tree: Tree, photograph. © W. S. Kelly, National Park Service.
Trichinosis: Trichnosis, photograph. JLM Visuals. Reproduced with permission.
Tropical cyclone: Hurricane Diana, photograph. U. S. National Aeronautics and Space Administration (NASA).
Tropical cyclone: Tropical cyclone, portrait. The Library of Congress.
Tropical cyclone: Tropical cyclone, depicted with maximum winds. National Oceanic and Atmospheric Administration.
Tropical Disease: Tropical disease, sore on arm, photograph. © Biophoto Associates, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Tropical diseases: Microscopic view of leishmania, photograph. © Alfred Pasteka/CNRI/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Tropical diseases: Tropical disease, spread through water, photograph. Hans & Cassidy. Courtesy of Gale Research.
True eels: Blackspotted Moray eel, photograph. JLM Visuals. Reproduced with permission.
Tsiolkovsky, Konstanin: Tsiolkovsky, Konstanin, portrait. The Library of Congress.
Tsunami: Tsunami engulfing building, photograph. © David Hardy/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Tumor: Tumors, lipoma, photograph. © James Stevenson/Science Photo Library, National Audubon Society/Photo Researchers, Inc. Reproduced with permission.
Hans & Cassidy.
Tumor: Tumor benign, malignant, illustration. Hans & Cassidy. Courtesy of Gale Research.
Tuna: Blue tuna swimming, photograph. © Y. Lanceau Jacana, National Audubon Society Collection/Photo Reasearchers, Inc. Reproduced with permission.
Tundra: Rocky Tundra, photograph. © E.R. Degginger, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Tundra: Rocky tundra, photograph. © E.R. Degginger, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Tungsten: Tungsten, photograph. © Russ Lappa/Science Source, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Tunneling: Tunneling, graph, energy vs. position, photograph. Courtesy of Gale Research.
Tunneling: Tunneling, distance vs. energy, illustration. Hans & Cassidy. Courtesy of Gale Research.
Turacos: Turaco birds, photograph. © Anthony Mercieca, National Audubon Society Collection/ Photo Researchers, Inc. Reproduced with permission

Turbine: Gas Turbine, photograph. © Brownie Harris/Stock Market. Reproduced with permission.
Turbulence: Ocean waves, cliff, photograph. JLM Visuals. Reproduced with permission.
Turkeys: Turkeys, photograph. Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Turtle: Turtle, photograph. © U.S. Fish & Wildlife Service
Turtles: Turtles, photograph. Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Tyrant flycatchers: Tyrant flycatchers, photograph. Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Ulcers: Ulcers, photograph. © Dopamine-CNRI, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Ultrasonics: Ultrasound image, photograph. Jacqueline Longe.
Ultraviolet Astronomy: Rosat prior to launch, photograph. © Domier Space/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Unconformity: Unconformity, Grand Canyon, photograph. JLM Visuals. Reproduced with permission.
Ungulates: Oryx eating grass, photograph. © Judd Cooney/Phototake NYC Reproduced with permission.
Uplift: Tilted strata, glacier, photograph. JLM Visuals. Reproduced with permission.
Uranium: Uranium disk, photograph. © Dept. of Energy, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Uranus: Uranus, elliptical, photograph. U. S. National Aeronautics and Space Administration (NASA).
Uranus: Uranus, controlled images, photograph. U. S. National Aeronautics and Space Administration (NASA).
Uranus: Uranus, photograph. U. S. National Aeronautics and Space Administration (NASA).
Uranus: Uranus, solar system, photograph. Hans & Cassidy. Courtesy of Gale Research.
Uranus: Uranus, diagram, illustration. Hans & Cassidy. Courtesy of Gale Research.
Urea: Urea, molecular structure, photograph. Hans & Cassidy. Courtesy of Gale Research.
Van Allen Belts: Van Allen Belts, Earth's magnetic field, photograph. U. S. National Aeronautics and Space Administration (NASA).
Van Allen belts: Van Allen Belts, daigram, magnetic lines of force, photograph. Hans & Cassidy. Courtesy of Gale Research.
Van der waals forces: Cholesterol molecule, photograph. © Jean-Claude Revy/Phototake NYC Reproduced with permission.
Vanadium: Vanadium, photograph. © Russ Lappa, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Vector: Vector, traingle, photograph. Hans & Cassidy. Courtesy of Gale Research.
Vector: Vector, acute angle, photograph. Hans & Cassidy. Courtesy of Gale Research.
Venus: Venus, photograph. U. S. National Aeronautics and Space Administration (NASA)..
Venus: Venus, gaseous traces, photograph. U. S. National Aeronautics and Space Administration (NASA).
Verreauxi Sifaka: Lemur, young propithecusberreauxi, photograph. © M. Loup, National Audubon Society Collection/ Photo Researchers, Inc. Reproduced with permission
Vertebrates: Two brown mountain sheep, photograph. © Yoav Levy/Phototake NYC Reproduced with permission.
Vicuna: Vicugna, photograph. © F. Gohier/ Science Source, National Audubon Society Collection/ Photo Researchers, Inc. Reproduced with permission

Video recording: Video Recording, diagram, photograph. Hans & Cassidy. Courtesy of Gale Research.
Video recording: Video recording, head and tape in contact with drum, photograph. Hans & Cassidy. Courtesy of Gale Research.
Viete, Francois: Viete, Francois, portrait. The Library of Congress.
Violet family (violaceae): Dual side of ginseng, woman bending, photograph. JLM Visuals. Reproduced with permission.
Viper: Popes pit viper, photograph. © Tom McHugh, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Vipers: Timber rattlesnake, mouse, photograph. JLM Visuals. Reproduced with permission.
Virchow, Rudolf Carl: Virchow, Rudolf Carl, portrait. The Library of Congress.
Vireo: Red-eyed Vireo, photograph. JLM Visuals. Reproduced with permission.
Virtual Reality: Virtual reality, man demonstrating, photograph. © Thomas Ernsting/Bikderberg/Stock Market. Reproduced with permission.

Virus: Herpes virus, photograph. © A. B. Dowsett/Science Photo Library, National Audubon Society Collection/ Photo Researchers, Inc. Reproduced with permission.
Virus: Virus, rod-like virus, icosahedral, asperical virus, illustration. Hans & Cassidy. Courtesy of Gale Research.
Virus: Virus, chart explaining replication, photograph. Hans & Cassidy. Courtesy of Gale Research.
Viscosity: Liquids, viscosity, photograph. © Yoav Levy/Phototake NYC. Reproduced with permission.
Vision: Vision, brain, eyes, field of vision, illustration. Hans & Cassidy. Courtesy of Gale Research.
Vision: Vision, diagram of brain, optic nerve, illustration. Hans & Cassidy. Courtesy of Gale Research.
Vision disorders: Corneal transplant, photograph. © Chet Szymecki/Phototake. Reproduced by permission.
Vitamin C: Vitamin C, micrograph, photograph. © Alfred Pasieka/Science Photo Library National Audubon Society Collection/Photo Researchers, Inc. Reproduced by permission.
Voit, Karl von: Voit, Karl von, portrait. The Library of Congress.
Volcano: Volcanic cinder cone, photograph. © Tom Bean/Stock Market. Reproduced with permission.
Volcano: Volcano Island, photograph. © Krafft, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Volcano: Portrait of Pu'u 'O' vent erupting on Lilauea's east rift zone. National Park Service.
Volcano: Eruption of Mt. St. Helens, photograph. JLM Visuals. Reproduced by permission.
Volume: Cheistry, flasks and beakers, photograph. © Peggy and Ron Barnett/Stock Market. Reproduced with permission.
Vulcanization: Vulcanization, sulfur links, photograph. Hans & Cassidy. Courtesy of Gale Research.
Vultures: Vultures eating aligator, photograph. JLM Visuals. Reproduced with permission.
Wald, George: Wald, George, portrait. The Library of Congress.
Walkingstick: Female walkingstick on leaf, photograph. © Alvin E. Staffan, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Wallace, Alfred Russel: Wallace, Alfred Russel, portrait. The Library of Congress.
Walnut family: Walnut tree, photograph. JLM Visuals. Reproduced with permission.
Walrus: Walruses, photograph. Charles Krebs/Stock Market. Reproduced with permission.
Warblers: Warblers, photograph. Robert J. Huffman/Field Mark Publications. Reproduced by permission.
Warblers, New World: Warblers, photograph. Robert J. Huffman/Field Mark Publications. Reproduced by permission.
Warburg, Otto: Warbury, Otto, photograph of sketch. The Library of Congress.
Wasps: Wasps, photograph. © George Bernard, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Waste Management: Waste Management, illustration. Robert J. Huffman/Field Mark Publications.
Waste Management: Recycling energy, crane, photograph. © Royal Greenwhich Observatory, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Water: Water, illustration. Robert L. Wolke. Reproduced by permission.
Water Hyacinth: Water Hyacinth, photograph. © Tom Carroll/Phototake NYC Reproduced with permission.
Water lilies: Lily pads, photograph. JLM Visuals. Reproduced with permission.
Water pollution: Water pollution, Hudson River, photograph. © Yoav Levy/Phototake NYC. Reproduced with permission.
Water treatment: Water treatment plant, man at railing, photograph. © Gabe Palmer/Stock Market. Reproduced with permission.
Waterwheel: Old Mill, Stone Mountain Park, photograph. © Chris Hamilton/Stock Market. Reproduced with permission.
Watt, James: Watt, James, photograph of painting. The Library of Congress.
Wave motion: Wave motion, photograph. © Martin Dohrn/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Wave Power: Wave power, wave in ocean, photograph. © Steve Wilkins/Stock Market. Reproduced with permission.
Waxbills: Blue breasted waxbill, photograph. © Elizabeth Lemoiney, National Audubon Society Collection/ Photo Researchers, Inc. Reproduced with permission
Waxwings: Waxwings, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced by permission.
Weasel: Long-tailed weasel, photograph. © Judd Cooney/Phototake NYC. Reproduced with permission.
Weather: Weather, photograph. © National Center for Atmospheric Research/University Corporation for Atmospheric Research/National Science Foundation 1337. Reproduced by permission.
Weather Forecasting: Weather forcasting, satellite, photograph. ©Tom Carroll/Phototake NYC Reproduced with permission.
Weather Forecasting: Weather forcasting, dopplar radar in Massachussetts, photograph. © Brownie Harris/Stock Market. Reproduced with permission.

Weather map: Weather map, photograph. JLM Visuals. Reproduced with permission.
Weathering: Weathering, photograph. © Richard Frear, National Park Service. Reproduced by permission.
Weaver: Weaver bird building nest, photograph. © Karl H. Maslowski, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Weinberg, Steven: Weinberg, Steven, portrait. The Library of Congress.
Welding: Computer controlled robot, photograph. © David Parker, 600 Group Fanuc/Science Photo Library, The National Audubon Society Collection/Photo Researchers. Reproduced with permission.
Weller, Thomas Huckle: Weller, Thomas Huckle, John F. Enders, portrait. The Library of Congress.
Werner, Alfred: Werner, Alfred, portrait. The Library of Congress.
Wes Jackson: Jackson, Wes, photograph. Terry Evans. Reproduced with permission.
Westinghouse, George: Westinghouse, George, portrait. The Library of Congress.
Wetlands: Wetlands, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced by permission.
Wexler, Nancy: Wexler, Nancy, photograph. The Library of Congress.
Whaling: Whaling, photograph. © Morgan, Greenpeace. Reproduced by permission.
Wheat: Wheat, photograph. JLM Visuals. Reproduced with permission.
Wheatstone, Charles: Wheatstone, Charles, portrait. The Library of Congress.
Wheel and axel: Wheel and axel, photograph. The Library of Congress.
Whipple, George Hoyt: Whipple, George Hoyt, portrait. The Library of Congress.
White dwarf: Symbiotic star, photograph. © Space Telescope Science Institute/NASA/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Whooping cranes: Whooping cranes, photograph. ©U.S. Fish & Wildlife Service.
Wieland, Heinrich: Wieland, Heinrich, portrait. The Library of Congress.
Wigner, Eugene Paul: Wigner, Eugene Paul, photograph. The Library of Congress.
Wild and Scenic Rivers Act: Wild and Scenic Rivers Act. Courtesy of U. S. Forest Service.
Wilderness: Wilderness, phototgraph. Courtesy of U. S. Forest Service.
Wilderness study area: Wilderness study area, photograph. Courtesy of U. S. Forest Service.
Wildfire: Wildfire, photograph. Robert J. Huffman/Field Mark Publications.
Wildfire: Wildfire, photograph. © Yuen-Gi Yee. Courtesy of U. S. Forest Service.
Wildfire: Wildfire, four illustrations, photograph. Hans & Cassidy. Courtesy of Gale Research.
Wildlife refuge: Wildlife refuge, photograph. © U.S. Fish & Wildlife Service.
Wildlife rehabilitation: Wildlife rehabilitation, photograph. © Merjenburgh, Greenpeace. Reproduced by permission.
Willow family: Willow family, photograph. James Lee Sikkema. Reproduced by permission.
Willow family: Willow family, photograph. Robert J. Huffman/Field Mark Publications. Reproduced by permission.
Willstatter, Richard: Willstatter, Richard, photograph of sketch. The Library of Congress.
Wilson, C. T. R.: Wilson, C. T. R., photograph of sketch. The Library of Congress.
Wind: Wind, photograph. National Oceanic and Atmospheric Administration.
Wind chill: Wind chill, graph, wind velocity, photograph. Hans & Cassidy. Courtesy of Gale Research.
Wind shear: Wind Shear, diagram, microburst, photograph. Hans & Cassidy. Courtesy of Gale Research.
Wind tunnel: Wind tunnel, photograph. U. S. National Aeronautics and Space Administration (NASA).
Wind tunnel: Wind tunnel, transonic tunnel, photograph. U. S. National Aeronautics and Space Administration (NASA).
Windaus, Adolf: Windaus, Adolf, portrait. The Library of Congress.
Wise use movement: Wise use movement. Courtesy of U. S. Forest Service.
Wohler, Friedrich: Wohler, Friedrich, portrait. The Library of Congress.
Wollaston, William Hyde: Wollaston, William Hyde, portrait. The Library of Congress.
Wolverine: Wolverine, photograph. © Tom Brakerfield/Stock Market. Reproduced with permission.
Wombat: Common wombat, photograph. © Bachman, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Wood: Wood, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Woodpecker: Woodpecker, photograph. JLM Visuals. Reproduced with permission.
Woodward, Robert Burns: Woodward, Robert Burns, portrait. The Library of Congress.
Wrens: Robert J. Huffman/Field Mark Publications.
Wright, Almroth Edward: Wright, Almroth Edward, portrait. The Library of Congress.
Wright, Wilbur and Orville: Wright, Wilbur, Wright, Orville, portrait. The Library of Congress.
X-ray astronomy: Supernova explosion, X-Ray, photograph. © Naval Research Laboratory/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
X-ray: X-Ray, woman being examinated, photograph. © Stock Market. Reproduced with permission.
X-rays: X-ray tube, illustration. Robert L. Wolke. Reproduced with permission.
Xenon: Radioactive xenon, lead containers, photograph. © Will & Deni McIntyre, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Yak: Yak eating grass, photograph. © Mark N. Boulton, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.

Yang, Chen Ning: Yang, Chen Ning, portrait. The Library of Congress.
Yeast: Magnified yeast, photograph. © Carolina Biological Supply/Phototake NYC. Reproduced with permission.
Yew: Yew, photograph. © James Lee Sikkema. Reproduced with permission.
Young, Thomas: Young, Thomas, portrait. The Library of Congress.
Yukawa, Hideki: Yukawa, Hideki, portrait. The Library of Congress.
Zebra: Zebra, photograph. © Robert J. Huffman/Field Mark Publications. Reproduced with permission.
Zeeman, Pieter: Zeeman, Pieter, portrait. The Library of Congress.
Zernike, Frits: Zernike, Frits, portrait. The Library of Congress.
Ziegler, Karl: Ziegler, Karl, portrait. The Library of Congress.
Zinc: Zinc, photograph. © Rick Altman, The Stock Market. Reproduced with permission.
Zirconium: Zirconium, photograph. © Russ Lappa/Science Source, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission.
Zooplankton: Zooplankton, chart, various types, illustration. Hans & Cassidy. Courtesy of Gale Research.
Zsigmondy, Richard: Zsigmondy, Richard, portrait. The Library of Congress.

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