68 



PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [DeC. 17, 





At present, 



with the 

 Gulf Stream. 



Differ- 

 ence. 



Without the 

 Gulf Stream. 



DiflFer- 

 ence. 



The Alps. 

 Temperature for January 



38F.\ 



73 J 

 55-5 



61 1 

 49-5 



36-5 F.\ 

 56 / 

 46-25 



30F."I 

 52 ■ 

 41 

 39 



o 



35 

 23 

 19-5 

 22 



34 F.I 



73 1 

 53-5 



23 F.I 

 61 ; 



42 



12F.\ 

 56 J 

 34 



-4F.1 

 46 ■ 

 21 



3°9 

 38 

 44 

 50 



„ ,, July 



Mean annual temperature 



Snowdon. 

 Temperature for January 





Mean annual temperature 



Northern Extremity op Scotland. 

 Temperature for January 



,. July 



Mean annual temperature 



Centre of Iceland. 

 Temperature for January 



„ July 



Mean 







14. The next case I have proposed for discussion is that in which 

 the Gulf-stream should exist, with a barrier of land connecting Scot- 

 land with Iceland, and that island with Greenland. Since this bar- 

 rier would intercept the influx of the Gulf- stream into the North 

 Sea, it would very much reduce the temperature there, and in all 

 the northern parts of Scandinavia. On the other hand, the waters 

 of the Gulf-stream, being now confined to the northern part of the 

 Atlantic, would considerably raise the temperature of that region. 

 According to our preceding estimate, the present increase of mean 

 annual temperature due to the Gulf-stream is as follows : — 



18° F. in Iceland; 



12°-25 F. in the north of Scotland 



'5 F. at Snowdon 



3° F. at the Alps. 



The mean annual temperature on the south coast of Iceland is now 

 aboat 40°. It is, I think, probable that this might be raised by 4° 

 or 5° in the case supposed, which would make it approximate to the 

 mean annual temperature of the English Channel. This effect on 

 the mean temperature would be due principally to the effect on the 

 winter temperature. If this latter were increased 6° or 7°, and the 

 summer temperature 2° or 3°, the January temperature would be 

 nearly uniform (or the January isothermal would run nearly north 

 and south) from Iceland to the latitude of the Alps or central France. 

 The January isothermal of 32° now runs north and south through 

 an equal extent of latitude from a point several degrees north of the 

 Arctic circle to the southern shore of the German Ocean. On the 



* This is deduced from the mean of the monthly temperatures. The mean 

 annual temperatures above given for the other cases is almost identical with those 

 deduced from the monthly temperatures. The discrepancy of 3° in the case of 

 Iceland may be attributed to local peculiarities. 



