492 CURRENTS AND WHALING. 



and Portugal, which current has been so disastrous by the. number 

 of vessels that have been wrecked on Cape Finisterre ; where it 

 divides, one branch of it passing around the shores of the Bay of 

 Biscay, along the west coast of France, and thence crossing the 

 English Channel, which is now well known as the Rennell Current; 

 while the main Polar Stream flows southward, along the coast of 

 Portugal towards Madeira, with a diminished velocity, as a surface 

 current. 



That the stream which sets upon Cape Finisterre is the origin 

 of the Rennell Current, the following remarks by Horsburgh clearly 

 show. 



" The current is found to set eastward, from March to November, 

 particularly when westerly winds prevail ; and off Cape Finisterre, 

 and near the south part of the Bay of Biscay, it sets mostly along 

 the coast to the eastward ; and along the east coast of the bay, it sets 

 to the northward, parallel to the west coast of France." 



At Madeira and the Canary Islands the surface Polar Stream ap- 

 pears to have ceased ; but by our observations on the deep-sea tempe- 

 rature, a submarine stream still appears to exist. In lieu of the former 

 we have the current familiarly known as the African Current, by its 

 causing so many distressing wrecks on that coast, and to which 

 attention has often been drawn by the captivity and cruel slavery to 

 which their crews have been subjected. 



As has been seen in the Narrative, but little surface current was 

 found on our voyage from Madeira to the Cape de Verdes; but 

 the submarine stream was still found, as was shown by the low 

 temperatures of the deep-sea soundings. At, and in the neighbour- 

 hood of the latter islands, and between them and Cape Verde on the 

 African coast, a strong surface current is felt. In endeavouring to 

 account for this remarkable circumstance of the creation of a current, 

 and its increased velocity, of which every navigator must be aware 

 when in the neighbourhood of many islands, and the effects of which 

 we have often experienced in our long voyage, I shall now advert to 

 the cause which I think is quite sufficient to produce the effect; and 

 that is the accumulation of water caused by the obstructions that 

 islands offer to the onward flow of submarine streams ; thus raising 

 the level of the ocean in their vicinity, and consequently a tendency 

 to run off, and thereby cause a current where none was perceptible 

 before, or an increased velocity in that which was felt. 



To this cause, then, I believe the currents around the Cape de 



