352 



THE GEOLOGIST. 



gists as to the former and extensive existence of glaciers, as 

 attested by striated and scored rocks, and thereby under- 

 mine a portion of the foundations of the theory of glacial 

 influences), our author seems to forget that water, being 

 superimposed upon the rocks, must contain the flinty par- 

 ticles acting upon them, and consequently, both the principal 

 and the agent would undergo the same change, and would 

 act and be acted upon reciprocally, in the same manner as 

 if the ordinary circumstances of their existence were undis- 

 turbed. The second point relates to the knotty subject of 

 the transformation of snow into ice, which many attribute 

 to the porous nature of that of which the glaciers are formed, 

 and the congelation of the water which they absorb during 

 the period when the solar influence melts the upper surface. 

 Our author, in this instance, objects to such an explanation 

 of the phenomena, which he says, takes place in regions 

 where the temperature is always below zero, as well as in 

 lower districts ; and he cannot conceive how the diminished 

 temperature in such cases can produce a result, for the com- 

 pletion of which, heat is an indispensible condition. In 

 opposition to this view, he quotes an opinion that the trans- 

 formation of the snow into ice takes place in the lower 

 portions of ravines containing glaciers, from the pressure of 

 the superincumbent quantity, and that the action is rendered 

 complete by the melting of the snowy particles, which takes 

 place from the caloric disengaged at the moment when the 

 weight compresses the separate crystals, and condenses the 

 air which is enclosed in this operation. This he deduces, to 

 all appearance, for the purpose of informing his readers of 

 the present theory of the conversion of the surface of the 

 snowy mass into a glacial covering, in order to demonstrate 

 his views ; but w^e waded through the pages, referring to 

 his conjectures with some little difficulty, and certainly with- 



