3C5 



expansive impulse into the atmosphere, would speedily arrive at a 

 region whence it would fall back in a frozen state. This would pro- 

 bably have taken place even in the summer season, at least in so far as 

 to load the mountain summits and valleys lifted above the line of per- 

 petual congelation. A change of climate having been effected by the 

 disruption of the crust, the winter influences would, for a long time, 

 have greater power, so that the whole surface within the sphere of 

 a cataclysm might have become covered with ice, until the crust 

 should begin to recover its temperature from the internal source of 

 heat, and the influence of the sun conjointly. The author supposed 

 that, on account of the surface having had, probably, but little ele- 

 vation previous to the cataclysm, the heat of the crust was so con- 

 siderable, as, joined to the influence of the sun, to be sufficient to 

 have induced on the temperate zone a climate more nearly allied to 

 that of the tropics, and such as to have admitted of the residence of 

 those animals requiring a comparatively warm climate, and whose 

 remains have given rise to much difficulty in geological speculations. 

 As a subsidiary source of vapour, the author supposed that at the 

 moment of the cataclysm, much water would have been admitted to 

 contact with the interior heated surface. He was not aware, at the 

 time he read his paper, that in a recent work by Charpentier on 

 glaciers, this geologist had appealed to the same thing as the only 

 source of the vapour ; so that the author's hypothesis of the es- 

 cape of pent up vapour, as the chief source for producing glaciers, 

 still remains his own ; and in conjunction with that of Charpentier, 

 it seems to furnish a theory of glaciers, which, in the present state of 

 discussion respecting glacial action, is a desideratum. 



2. Geological Notes on the Alps of Dauphine. By Professor 



Forbes. Part 2d. 



The district proposed to be described, in so far as it was studied 

 by the author in two joui-neys in 1839 and 1841, is an out- Iyer or 

 appendage to the main Alpine chain, which occupies a considerable 

 portion of the old province of Dauphine, and the modern depart- 

 ments of the Hautes Alpes and Iserc. It is bounded, roughly, by tho 

 rivers Arc and Isere on the north, and by the Durance and the Drac 

 in other directions. Its nucleus is essentially granitic, against which 

 se<limcntary deposits of limestone, of different ages, and especially 

 of lias and chalk, repose in highly elevated or contorted strata ; and 



