32.1: THE PHYSICAL GEOGRAPHY OF THE SEA. 



and the moment the unwonted pressure is removed the liquid 

 cushion is restored, and there is again compensation. 



600. The discovery of this arrangement in the oceanic ma- 

 The causes that pro- chiuerj suggcsts that the streams of running water 

 iTresSrnea? Us ^^ ^^^ sca play rather about its surface than in its 

 surface. depths ; that the causes which produce currents 

 reside at and near the surface; that they are changing heat and 

 alternating cold with their powers of contraction and expansion — 

 winds and sea-shells with evaporation and precipitation ; and it 

 is certain that none of these agents appear capable of reaching 

 very far down into the depths of the great and wide sea with their 

 influences. They go not much, if any, farther down than the 

 light can reach. On the other hand, the most powerful agents in 

 the atmosphere reside at and near its bottom ; so that, where these 

 two great oceans meet — the aqueous and the aerial — there we 

 probably have the greatest conflict and the most powerful display 

 of the forces that set and keep them in motion, making them to 

 rasre and roar. 



o 



601. The greatest depth at which running water is to be found 

 Their depth, in the sca is probably in the narrowest part of 



the Gulf Stream, as, coming from its mighty fountain, it issues 

 through the Florida Pass. The deep-sea thermometer shows that 

 even here there is a layer of cold water in the depths beneath, 

 so that this " river in the sea" may chafe not against the solid 

 bottom. What revelations of the telescope, what wonders of the 

 microscope, what fact relating to the physical economy of this 

 terrestrial globe, is more beautiful or suggestive than some of the 

 secrets which have been fished up from the caverns of the deep, 

 and brought to light from the hidden paths of the sea ? 



602. In my researches I have as yet found no marks of running 

 The cushion of still watcr imprcsscd upon the foundations of the sea 



witGr I, its thick* 



"esa. beyond the depth of two or three thousand feet. 



Should future deep-sea soundings establish this as a fact in other 

 seas also, it will prove of the greatest value to submarine tele- 

 graphy. What may be the thickness of this cushion of still wa- 

 ter that covers the bottom of the deep sea is a question of high in- 

 terest, but we must leave it for future investigation. 



603. In Chapter X. {The Salts of the Sea), I have endeavored 

 to show how sea-shells and marine insects may, by reason of the 



