CURRENTS AND WHALING. 499 



into two branches, one of which sets along the west coast of South 

 America, far to the northwards. 



The main stream enters the Atlantic, and in the vicinity of Cape 

 Horn is almost as well known as the Gulf Stream on our own coast. 

 It appears to be strongest in the months of August, September, and 

 October, the spring of that hemisphere, and weakest in April and 

 May, or the autumn. It continues its course to the northeast until 

 it appears lost in the South Atlantic, probably sinking beneath the 

 warmer water that has been flowing- along the coast of Brazil. Our 

 observations made its greatest velocity seventy-two miles in twenty- 

 four hours, in a direction east-northeast, but its usual rate is about 

 thirty miles in the same time. 



One remarkable feature of the water in the neighbourhood of Cape 

 Horn is its very low temperature at great depths. We found it, as 

 has been stated in Chapter V., as low as 28°, at the depth of four 

 hundred fathoms ; and although this great depression of temperature 

 was not exactly verified by other observations, yet those made in the 

 vicinity were sufficiently low to render this remarkable fact probable. 



That the direction of a great body of waters to the northward 

 and eastward, is not confined to the vicinity of Cape Horn, we have 

 one proof in the drift of the icebergs, even beyond the line at which a 

 current is found at the surface, and which must therefore be carried 

 by submarine streams ; and another in the observations made by the 

 late French expedition under D'Urville, who found a current setting 

 east-northeast, along the icy barrier to the south of Powell's Group. 



It has been stated that the northeast Polar Stream is divided into 

 two branches at Cape Horn. The Chili branch of the stream at first 

 retains the northeast direction, and sets upon the coast of that country, 

 but as it advances it takes a direction more towards the north. This 

 stream is not superficial merely, but prevails to a great depth, or is sub- 

 marine. This fact is conclusively shown by an observation of Captain 

 Du Petit Thouars in the French frigate Venus in 1837; he found in 

 making a deep-sea sounding in this stream during a calm, that the 

 line continued to hang vertical during the whole three hours that the 

 observation continued. He justly ascribes this occurrence to the 

 motion of the whole body of water to the north with an equal velocity. 

 The set towards the coast in the more southern portion of the stream 

 is shown by the frequent wrecks on the coast of Chili, and the diffi- 

 culty which vessels leaving Valparaiso to double Cape Horn experi- 



