OCEANOGRAPHY 405 



knowledge of the ocean advanced with more rapid steps than ever 

 before. At first this knowledge only extended to the surface, 

 the comparative area of oceans, their principal currents, and the 

 general distribution of temperature. In the middle of the last 

 century Maury collected all that was known, and drew charts of 

 the currents and winds for the assistance of navigation. This was 

 the beginning of the scientific study of the oceanic waters; at 

 that time the conditions below the surface were still little known. 

 A few investigations, some of them valuable, had been made of 

 the sea fauna, even at great depths, but very little had been done 

 towards investigating the physical conditions. It was seen, how- 

 ever, that there was here a great field for research, and that there 

 were great and important problems to be solved; and then, half a 

 century ago, the great scientific expeditions began, which have 

 brought an entire new world to our knowledge. 



It is only forty years since the Challenger sailed on the first 

 great exploration of the oceans. Although during these forty 

 years a quantity of oceanographical observations has been col- 

 lected with a constant improvement of methods, it is, nevertheless, 

 clear that our knowledge of the ocean is still only in the pre- 

 liminary stage. The ocean has an area twice as great as that 

 of the dry land, and it occupies a space thirteen times as great as 

 that occupied by the land above sea-level. Apart from the great 

 number of soundings for depth alone, the number of oceanographical 

 stations — with a series of physical and biological observations at 

 various depths — is very small in proportion to the vast masses 

 of water; and there are still extensive regions of the ocean of the 

 conditions of which we have only a suspicion, but no certain 

 knowledge. This applies also to the Atlantic Ocean, and especi- 

 ally to the South Atlantic. 



Scientific exploration of the ocean has several objects. It seeks 

 to explain the conditions governing a great and important part of 

 our earth, and to discover the laws that control the immense masses 

 of water in the ocean. It aims at acquiring a knowledge of its 



