382 THE DEPTHS OF THE SEA. [CHAP. vin. 



received from the sun by the Arctic regions, and, 

 reduced by a half to avoid all possibility of exaggera- 

 tion, it is still equal to one-fifth of the whole amount 

 received from the sun by the entire area of the North 

 Atlantic. The Gulf- stream, as it issues from the Strait 

 of Florida and expands into the ocean on its north- 

 ward course, is probably the most glorious natural 

 phenomenon on the face of the earth. The water is 

 of a clear crystalline transparency and an intense 

 blue, and long after it has passed into the open sea it 

 keeps itself apart, easily distinguished by its warmth, 

 its colour, and its clearness ; and with its edges so 

 sharply defined that a ship may have her stem in 

 the clear blue stream while her stern is still in the 

 common water of the ocean. 



" The dynamics of the Gulf-stream have of late, 

 in the work of Lieutenant Maury already mentioned, 

 been made the subject of much (we cannot but think 

 misplaced) wonder, as if there could be any possible 

 ground for doubting that it owes its origin entirely 

 to the trade-winds." x Setting aside the wider ques- 

 tion of the possibility of a general oceanic circulation 

 arising from heat, cold, and evaporation, I believe 

 that Captain Maury and Dr. Carpenter are the only 

 authorities who of late years have disputed this 

 source of the current which we see, and can gauge 

 and measure as it passes out of the Strait of Florida ; 

 for it is scarcely necessary to refer to the earlier 

 speculations that it is caused by the Mississippi river, 

 or that it flows downwards by gravitation from a 

 ' head ' of water produced by the trade-winds in the 

 Caribbean sea. 



1 Herscliel, op. cit. p. 51. 



