The navigational needs are fairly obvious. A deep-running 

 submarine in an underwater jet stream (and there may be such), 

 or a submarine in the region of shear between a current and the 

 counter current can be set off course unexpectedly and perhaps 

 tossed about. We do not know. We do not have a good method of 

 measuring deep currents. 



We need to know about DEEP SEA FLOOR CHARACTERIS- 

 TICS; people in our sister Bureau of Yards and Docks ask ques- 

 tions similar to those a builder on land would ask, such as: What 

 is the bearing strength of the sediments at this spot? How far 

 down from the bottom is bed rock? What is the expected "windage" 

 (horizontal pressure due to currents) on future structures? 



I would like to include a few generalities as to materials at 

 this point. The first rule in choosing materials for underwater 

 work is: "take nothing for granted. " You are working in a 

 strange environment -- both salt water and salt atmosphere. 

 During the war, when the radio industry began to manufacture 

 fleet units of sonar equipment, I recall beautiful receivers which 

 had undoubtedly stood up perfectly under hours of the bench 

 testing your home radio would require. But the first time a 

 little spray came through the porthole, some of the condensers 

 turned green, perhaps from sea sickness, and the receiver went 

 dead. Whole systems were knocked out. Just to emphasize the 

 proper choice of materials, here is a verbatim comment regarding 

 a material which most of us sort of "gravitate to, " as you might 

 say "natxirally. " It seems so reasonable to use stainless steel in 

 connection with water -- perhaps because of those lovely knives 

 and forks of which your wife is so proud! "Care should be taken 

 with the use of stainless steels in seawater atmospheres. Class 

 304L or 316 are recommended for moving and stagnant water con- 

 ditions, respectively, to avoid chromium carbide formation which 

 leads to pitting. " 



Each instrument developer must carefully consider the ma- 

 rine environment and the effects of corrosion and antifouling. 

 Sometimes a less exotic material with a good paint may be the 

 better and more economical way to do it. In particular, little is 

 known about the effects of the so-called "trace elements" in sea 

 water. Yet they are beconning important in antifouling and 

 corrosion prevention. 



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