E. MINERALOGY AND GEOLOGY. 139 



maintain itself on the north side of the Gnlf of St. Lawrence, 

 and to extend as far as the latitudes of Murray Bay and 

 Gaspe. South of Gaspe we have the warmer New England 

 fauna of Northumberland Strait. Some of the peculiarities 

 of the post-pliocene fauna in comparison with that of the St. 

 Lawrence River indicate a considerable influx of fresh wa- 

 ter, derived possibly from melting ice and snow. Dawson's 

 Notes, 101, 102. 



GLACIAL PERIOD OF THE NORTHERN HEMISPHERE. 



Mr. James Geikie has lately published an elaborate article 

 upon the successive changes of climate experienced in Great 

 Britain, especially during the glacial epoch ; and among some 

 of the more general conclusions at which he has arrived are 

 the following : 



1. That at some distant period (according to Mr. CrolPs 

 calculations, upward of 200,000 years ago), owing to the ec- 

 centricity of the earth's orbit being at a high value, and the 

 winter of our hemisphere happening to fall in aphelion, a cli- 

 mate of intense severity covered Scotland, Ireland, and the 

 major portion of England with a massive sheet of snow and 

 ice. At the same time similar conditions characterized the 

 mountains and northern regions of Europe and America. 



2. That one result of this glacial action was the erosion of 

 rock-basins. 



3. That intense glacial conditions were interrupted by in- 

 tervening periods characterized by mild and even genial cli- 

 mates, the changes of climate being directly due to the pre- 

 cession of the equinoxes, which during a period of extreme 

 eccentricity would gradually cause the ice-cap to shift from 

 one pole to the other. 



4. That these interglacial climates are represented in Scot- 

 land by stratified deposits intercalated with the till, and con- 

 taining, in places, mammalian and vegetable remains ; in En- 

 gland by beds in the boulder clay, and by some portions of 

 the valley gravels and cave deposits, with paleolithic imple- 

 ments and bones of the extinct mammalia; on the Continent 

 by similar deposits ; in America by layers of peat, with bur- 

 ied trees and extinct mammalia, 



5. That the climate of the earlier cold periods was more 

 severe than in subsequent glacial periods of the same great 

 cycle. 



