and its Physical Relations to the Glacial Epoch. 123 



it would otherwise be were it not for the influence of the Gulf- 

 stream *. A reduction of the Gulf-stream to one-half its pre- 

 sent volume would lower the temperature of the centre of Scot- 

 land about 1-4°. 



According to column V. the temperature of this country 

 850,000 years ago, owing to the greater distance of the sun at 

 midwinter, would be lowered 45°'3. Now add 14° for the di- 

 minution of the Gulf-stream, and we have 59°*3 below the pre- 

 sent midwinter temperature, or — 20 o, 3 as the midwinter tem- 

 perature of the centre of Scotland at that period. Assuming, 

 then, that the diminution of the Gulf-stream was propor- 

 tionate to the extent of the excentricity, column VII. gives the 

 actual midwinter temperature of the centre of Scotland at the 

 corresponding periods. 



The difference between the midwinter temperature of Scot- 

 land at some of those periods and its present is certainly great. 

 But there is, however, nothing extravagant or unlikely in sup- 

 posing the existence of so low a temperature during the glacial 

 epoch when we reflect that at the present day there are places 

 on the same parallel of latitude as Scotland which have a mid- 

 winter temperature nearly as low as any indicated in the Table : 

 for example, at the Cumberland House in North America, 

 situated in a lower latitude than the south of Scotland, the 

 present midwinter temperature is upwards of 13° below zero. 



That the cold of the glacial epoch in Scotland was to a con- 

 siderable extent due to a stoppage, or at least great diminution, 

 of the Gulf-stream, is attested, I think, by the fact pointed out 

 by the Rev. Mr. Crosskey from a comparison of the fossils of 

 the glacial beds of Canada with those of the Clyde, that the 

 change of climate in Canada since the glacial epoch has been 

 far less complete than in Scotland f. The American continent 

 was no doubt, during the glacial epoch, as cold as, if not colder 

 than the continent of Europe; but then, if the Gulf-stream 

 was stopped during the glacial epoch, the rise of temperature 

 which would follow on the return of the stream at the close of 

 that epoch would be greater in Scotland and all over the 

 western shores of Europe than in America. 



It might be thought that if the winters had been so much 

 colder at the periods in question than at present, owing to the 

 sun's greater distance during that season, the summers, on the 

 other hand, ought to have been so much warmer, owing to the 

 sun's greater proximity. About 850,000 years ago the winters, 

 according to the Table, were 45° colder than at present ■ and 



* See Dove ' On the Distribution of Heat over the Surface of the 

 Globe/ Map V. 



t Transactions of the Glasgow Geological Society for 1866. 



