Ix 



PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



1 . The configuration of land and sea the same as at present, but 

 without the Gulf-stream. 



2. The Gulf-stream the same as at present, except that its progress 

 into the North Sea is supposed to be arrested by a barrier of land, 

 extending from the north of Scotland to Iceland, and thence to the 

 coast of Greenland. 



• 3. The basin of the Atlantic from the Tropic to the North Sea 

 converted into land, uniting the old and new continents. 



4. Large portions of the continents of Europe and North America 

 submerged beneath the surface of the ocean, and the Gulf-stream di- 

 verted into some other course. 



By a study of Dove's admirable map of isothermal lines, we easily 

 recognize the masses of land in the northern parts of the old and new 

 continents, and the Gulf-stream as the principal causes of the ab- 

 normal forms of the isothermals in the higher latitudes of the north- 

 ern hemisphere. In like manner the irregular forms of the known 

 isothermals of the southern hemisphere, extending to about the lati- 

 tude of 50°, may be seen to be attributable to similar causes, more 

 especially, perhaps, in this case to well-known ocean-currents ; and a 

 knowledge of these causes enables us to draw the isothermals in such 

 hypothetical cases, as those above-stated, with approximate accuracy. 

 This is what I have first attempted to do in the memoir before us. 



Taking the first case, I arrive at the results embodied in the fol- 

 lowing table : — 





At present, 



with the 

 Gulf stream. 



DiflFer- 

 ence. 



Without the 

 Gulf stream. 



Differ- 

 ence. 



The Alps. 

 TemBerature for January 



38F.1 

 73 1 

 55-5 



38F.1 

 61 / 

 49-5 



36-5 F."l 

 56 J 

 46-25 



30 F. I 

 52 / 

 41 

 39 



35 

 23 

 19-5 

 22 



34F.1 

 73 1 

 53-5 



23F."I 

 61 1 

 42 



12F.1 

 56 / 

 34 



-4F.\ 

 46 / 

 21 



39 

 38 

 44 

 50 







Snowdon. 



July 





Northern Extremity of Scotland. 



Julv 



Mean annual temnerature 



Centre of Iceland. 

 Temperature for January 







Mean annual temnerature* 





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

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

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

 Iceland may be attributed to local peculiarities. 



