Mr Miirchisou on tU Glacial Theory. IM 



fi^und that ice can produce sucli cfiects ; aud in the same breath ^e ar< 

 told that beds of shells have been placed on a mountain by an agency 

 which is truly supernatural. 



In fact the '' glacier" theory, as extended by its author, in proving too 

 much, may be said to destroy itself. Let it be limited to such effects as 

 are fairly deducible from the Alpine phenomena so clearly described by 

 Agassiz, and we must all admire in it a vera causa of exceeding interest ; 

 but once pass the bounds of legitimate induction from that vera causa, 

 and try to force the manj' and highly diversified superficial phenomena 

 of the surface of the globe, into direct agreement with evidences of the 

 action of ice under the atmosphere, and you will be driven forward like 

 the ingenious author of the theory, so to apply it to vast tracts of the 

 globe, as in the end to conduct you to the belief, that not only both 

 northern and southern hemispheres, but even quasi tropical regions, 

 were shut up during a long period in an icy mantle. Once grant to 

 Agassiz that his deepest valleys of Switzerland, such as the enormous 

 chasm of the lake of Geneva, were formerly filled with solid snow and 

 ice, and I see no stopping-place. From that hypothesis you may pro- 

 ceed to fill the Baltic and Northern Seas, cover Southern England, and 

 half of Germany and Russia with similar icy sheets, on the surfaces of 

 which all the northern boulders might have been shot off But even 

 were such hypotheses granted, without we also build up former moun- 

 tains of infinitely greater altitude than any which now exist, we have no 

 adequate centres for the construction of enormous glaciers which ima-* 

 gination must create in many regions to account for the phenomena. 

 The very idea which records the existence of these vast former sheets of 

 ice is at variance with all that is most valuable in the works of Charpen- 

 tier, Venetz, and Agassiz, whose data, as carefully eliminated from Al- 

 pine phenomena alone, would naturally teach us never to extend theit 

 application when those conditions are absent, viz. the mountain chain> 

 by the very presence of which the phenomena arc explained. 



But though the Alpine glacial theory be new, the scratches and polish-* 

 ed surfaces of rocks arc by no means of recent observation. Many 

 Swedish miners, from the days of Tilas and Bergman, failed not to re- 

 mark how their mountain sides were furrowed, and in our own times, 

 Sefstrom* of Sweden, and Bohtlingkt of Russia, have not only narrowly 

 traced them over wide regions, but have endeavoured to account for 

 them. The first of these authors remarked, that nearly all the hard rocks 

 of this country had a " worn or weather side," and a highly escarped or 

 " lee side," the former being exposed to the north and the latter to the 

 south ; and having further shewn that the detritus had generally been 

 carried from N. to S., he called the worn face the " weather side," and 

 the higher and jagged extremity of such ridges the " lee side." Extend- 

 ing his observations to many hundred places, he divided these scratches 

 into what he calls normal and s^ide furrows, shewing that in the latter 



* Sec Taylor's Scientific Memoirs^ vol. iii. p. 81, 

 t Jamecon's Journal, vol. %xx\. p. 253. 



