The Structure of the Atlantic : 31 



comparative shallowness of the oceans but neither he nor his inter- 

 preters seem to have made an effort to convey to the general reader 

 how shallow the oceans really are. 



It is easy enough to understand how this situation has arisen. A 

 man swimming from a sandy beach may properly say the ocean is 

 deep when he can no longer touch bottom. A primitive man sailing 

 in a canoe will say the ocean is deep when the irregular stone sus- 

 pended from a thong that he lets down from the bow of his vessel 

 will no longer take hold on the bottom. A fisherman on the Grand 

 Banks may properly think that the waters in which he is fishing are 

 pretty deep if he has tried for a sounding with his lead line and 

 missed bottom. 



Up to a few years ago all ocean depths were measured, even from 

 research vessels, by letting down a heavy weight at the end of a long 

 line payed out from a stationary or drifting ship until the weight 

 actually reached the bottom of the ocean. This required infinite pa- 

 tience, skill, knowledge, good fortune with the weather and a gener- 

 ous amount of time. The student of the sea who made such sound- 

 ings could understandably say that from his point of view the ocean 

 was deep. 



In recent years all this has changed. Methods have been invented for 

 measuring the oceans and the seas by bouncing sonic and supersonic 

 waves to the bottom of the ocean. The waves are created at the ship 

 or the station and the length of time that it takes them to reach the 

 ocean bottom and return gives a measure of the depth which may be 

 read almost instantly and continuously. The result is that the map- 

 ping of the ocean floor has recently gone on at a terrific pace and has 

 rapidly built up a fairly accurate knowledge of the shape and depths 

 and limits of the ocean basins. 



Of course, even before this had happened, the oceanographers had 

 a good general idea of the depth of the oceans and they already knew 

 that compared with the size of the earth and to the vast extent of the 

 oceans, they were in fact very thin and shallow bodies of water. I am 

 a great admirer of the oceanographers and an enthusiastic follower of 

 the work that they are doing and nothing that I say here is intended 

 in any way to diminish the credit and the support which they deserve 

 from the public. Still I cannot help wishing that they and the more 

 popular writers had done a little more to let the general public in on 

 a trade secret. In an astronomical or geographical sense the oceans are 

 very shallow. 



In part the oceanographers are victims of two of their own profes- 



