THE GULF STREAM. 199 



assign their origin ; and I cannot but think that the 

 Biscay and Guinea currents, as well as the current 

 which flows into the Mediterranean through the Straits 

 of Gibraltar, are as truly bifurcations of the Gulf 

 Stream as the current which laves the shores of Ireland 

 and Sweden. 



There will be noticed also in the map three return 

 streams, one flowing southward outside Iceland, another 

 sweeping round the eastern shores of Greenland, and 

 the third flowing through Baffin's Bay and Davis's 

 Straits. The two last unite south of Davis's Straits, and 

 flow on together to meet the first stream outside New- 

 foundland, whence the three flow as a single current 

 past the shores of the United States. It is generally 

 assumed, and in all probability justly, that these three 

 streams are derived from the Gulf Stream, and are 

 different branches of its returning waters. 



Between the single return-stream which laves the 

 shores of the United States and the Gulf Stream there 

 is an unshaded space in the map. It is not to be in- 

 ferred, however, that this space represents still (or 

 rather unflowing) water. On the contrary, it is the 

 c debatable ground ' between the opposite currents. In 

 spring the whole of this space is occupied by the south- 

 ward flowing waters of the cold return-current. In 

 autumn the whole of the space is occupied with the 

 waters of the Gulf Stream. Backwards and forwards 

 over this space the rival currents are continually sway- 

 ing, the period of an oscillation being one year. 



In the widest part of the Atlantic Ocean that, 



