Mild Polar Climates. 271 



cient to prevent the formation of permanent ice, was all that 

 was really necessary ; for were it not for the presence of ice 

 the summers of Greenland would be as warm as those of 

 England. 



Were the whole of the warm water of the Gulf-stream at 

 present to flow into the Arctic Ocean, it would probably re- 

 move the ice of Greenland. Any physical changes, such as 

 those that have been discussed on former occasions, which 

 would greatly increase the volume and temperature of the 

 stream and deflect more of its waters into the Arctic Ocean 

 would, there is little doubt, confer on the polar regions a 

 climate suitable for plant and animal fife. At present the 

 Gulf-stream bifurcates in mid- Atlantic, one branch passing 

 north-eastwards into the Arctic regions, whilst the larger 

 branch turns south-eastwards by the Azores, and after passing 

 the Canaries reenters the equatorial current. As the Gulf- 

 stream, like other great currents of the ocean, follows almost 

 exactly the path of the prevailing winds *, it bifurcates in mid- 

 Atlantic simply because the winds blowing over it bifurcate 

 also. Any physical change which would prevent this bifurca- 

 tion of the winds and cause them to blow north-eastwards 

 would probably impel the whole of the Gulf-stream waters 

 into the Arctic seas. All this doubtless might quite well be 

 effected without any geographical changes, although changes 

 in the physical geography of the North Atlantic might be 

 helpful. 



These considerations regarding the influence of the Gulf- 

 stream point to another result of an opposite character. It 

 is this : if a large increase in the volume and temperature of 

 the stream would confer on Greenland and the Arctic regions 

 a condition of climate somewhat like that of North-western 

 Europe, it is obvious, as has been shown at length on former 

 occasions, that a large decrease in its temperature and volume 

 would, on the other hand, lead to a state of things in North- 

 western Europe approaching to that which now prevails in 

 Greenland. A decrease leads to a glacial, an increase to an 

 interglacial condition of things. 



Sir William Thomson on Mild Arctic Climates. — In a paper 

 read before the Geological Society of Glasgow in February 

 1877, Sir William maintains also that an increase in the 

 amount of heat conveyed by ocean-currents to the Arctic 

 regions, combined with the effect of Clouds, Wind, and 

 Aqueous Vapour, is perfectly sufficient to account for the 

 warm and temperate condition of climate which is known to 



* See ' Climate and Time,' p. 213. 



