Page 2 U. S. Navy (USN) 3 University of Pennsylvania Museum—National Geographic Expedition 5 USN 6 Woods Hole Oceanographic Institution (WHOI) 7 Diagram, WHOI; photo, S. Hull 9 Top, Oregon State University (OSU); bottom, University of California, San Diego, Scripps Institution of Oceanography (SIO) 10 Lamont Geological Observatory of Columbia University 12 USN 15 SIO 19 R. H. Backus. _Physics Today_ (November 1965), “Sound Reflections In and Under Oceans,” J. B. Hersey 20 U. S. Bureau of Commercial Fisheries Biological Laboratory, Honolulu, Hawaii 22 USN 24 Laboratory of Radiation Biology, University of Washington (LRB) 26 Jan Hahn 27 Franklin GNO Corporation 28 George D. Grice, WHOI 31 SIO 33 OSU 35 Monsanto Research Corporation 37 USN 38 Lane-Wells Company 39 Research Triangle Institute 43 USN 46, 47 & 48 Martin-Marietta Company 49 The Photo Mart 53 Top, Metropolitan Water District of Southern California; bottom, Bechtel Corporation 55 U. S. Bureau of Commercial Fisheries, Fish and Wildlife Service; inset, Brookhaven National Laboratory 56 Norsk Folkemuseum, Oslo, Norway, courtesy The Mariners Museum, Newport News, Virginia 57 National Science Foundation 61 S. Hull Cover photo courtesy James Butler, USN Author’s photo courtesy General Dynamics Corporation Frontispiece from Jan Hahn THE COVER [Illustration: The ATOM and the OCEAN] The ship on the cover is the trim _Atlantis_ riding the waves about 200 miles south of Bermuda. The first craft built by the United States as an oceanographic research vessel, she traveled more than 1,200,000 miles across the seven seas for a period of 30 years. She “ran” over 6000 hydrographic stations and was used for innumerable dredging, coring, biological, physical, and acoustical research operations. After she was retired from active service at the Woods Hole Oceanographic Institution in Massachusetts, she was sold to Argentina, where she has resumed her role as an oceanographic research vessel. THE AUTHOR E. W. SEABROOK HULL is an experienced writer and editor in technical and engineering fields. He is the author of _The Bountiful Sea_, published in 1964 by Prentice-Hall, and _Plowshare_, another booklet in this Understanding the Atom Series. He is the editor of _Ocean Science News_ and editor and publisher of _GeoMarine Technology_. [Illustration: E. W. Seabrook Hull] Footnotes [1]For a description of how these will work, see _Controlled Nuclear Fusion_, another booklet in this series.