Ix. PRESIDENT'S ADDRESS. 



sediments exhibiting great diversities may not only be strictly 

 contemporaneous in time, but also closely approximate. Thus the 

 law of distribution of species presents itself in a very unstable 

 aspect, when it is seen to depend on a slight physical change, but 

 quite enough to deflect a current. Some marine area must be 

 chosen to attain a continuous and complete record of the history of 

 life upon any given portion of the globe, the surface of which has 

 been for a long period of time uninterruptedly occupied by the sea. 

 Such areas are supposed to exist in the abyssal depth of the ocean ; 

 if so, all the conditions for a perfect continuity of life would be 

 present in that area. 



Until the expedition of " The Challenger " and that of the 

 " Fram " it was supposed that a uniform or approximately uniform 

 temperature prevailed at the greatest depths in every latitude. Dr. 

 Nansen found in the Polar basin warm water at a temperature 

 higher, more briny, and clearly originating from the warmer 

 current of the Gulf Stream, diving under the colder, but lighter, 

 and less briny water of the Polar Sea, thus dissipating the hitherto 

 entertained idea that a low uniform temperature invariably 

 prevails at the greatest depths in every latitude, and was a part 

 and consequence of a general system of oceanic circulation. The 

 permanent low temperature of the bottom water of the sea at great 

 depths would impose limits for the migration of species as equally 

 effective as the highest ranges of mountains upon land, and such a 

 condition of things no doubt exists in areas not affected by the 

 Gulf Stream. The great importance of dredging was recognised 

 about 50 years ago. Previous to that date, the little that was 

 known of the inhabitants of the sea was not much beyond low- 

 watermark, and seems to have been gathered almost entirely from 

 the objects thrown up on the beach after storms, or from chance 

 captures by fishermen or in trawls. The naturalist's drsdge seems 

 never to have been used for a systematic investigation of the fauna 

 at the bottom of the sea. At the Birmingham meeting of the 

 British Association in 1839 a committee was appointed "for 

 researches with the dredge with a view to the investigation of the 



