6. BRIEF HISTORICAL BACKGROUND IN THE DEVELOP- 

 MENT OF OCEANOGRAPHIC INSTRUMENTS, PRESENT 

 STATE OF THE ART, AND SOME NEW CONCEPTS 



James M. Snodgrass 



Scripps Institution of Oceanography 

 La Jolla, California 



It is rather difficult to know precisely what to say to a group 

 of this sort. This is partly due to the tremendous spread of 

 knowledge which you represent. Fvirthermore, I see a very large 

 number of familiar faces in the audience. Some of the things 

 which I am going to say you may well have heard before. Please 

 excuse iny repetition, but it is principally for the benefit of those 

 who do not have the information you possess. 



Some of the things which I shall choose to say are perhaps 

 controversial. If so, I assure you that I have done this on pvirpose. 

 I will attempt to give you some idea of the thinking that has gone 

 into the development of oceanographic instruments, the nature of 

 the background, principally the ocean environment, and the prob- 

 lems which the environment poses. Admiral Pierce mentioned the 

 enormity of the problem. It is a truly challenging one. 



Some idea of our problem can be gathered by the fact that 80 

 percent of the Pacific Ocean is over 3,000 meters deep. This 

 corresponds roughly to a pressure of 4, 300 p. s.i. (pounds per 

 square inch). Some 27 percent of the Pacific Ocean, for instance, 

 has depths in excess of 5, 000 meters, which means that instru- 

 ments near the bottom must be designed to withstand pressures in 

 excess of 7,000 p. s.i. Further, there is an almost ridiculous con- 

 trast between the velocities which our oceanographic instruments 

 must measure cind those in the aerospace field. Manned vehicles 

 nneasure velocities in Mach numbers; guided missiles and 'slmilaj: 

 devices measure them in miles per second; while in the field of 

 oceanography it is often necessary to measxire velocities in centi- 

 meters per second. 



For the sake of understanding better the scale of the problem, 

 I will use an analogy that I credit to Mr. Thomas A. Manar of 



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