The Glacial Them-y. 585 



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 sucli 

 effects as are fairly deducible from the Alpine phcenomena 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 induc- 

 tion from that vera causa, and try to force the many and highly 

 diversified supei-ficial phaenomena 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 proceed 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 mountains of infinitely greater altitude than any 

 which now exist, we have no adequate centres for the construc- 

 tion of enormous glaciers which imagination 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 Charpentier, Venetz, and 

 Agassiz, whose data, as cai'efuUy eliminated from Alpine phaeno- 

 mena alone, would naturally teach us never to extend their appli- 

 cation when those conditions are absent, viz. the mountain cliain, by 

 the very presence of wliich the phaenomena are explained. 



But thougli the Alpine glacial theory be new, the scratches and 

 polished surfaces of rocks are by no means of recent observation. 

 Many Swedish miners, from tlie days of Tilas and Bergman, failed 

 not to remark how their mountain sides were furrowed, and in our 

 own times, Sefstrdm* of Sweden, and Bdhtlingk of Russia, have not 

 only narrowly traced them over wide regions, but have endeavoured 

 to account for them. The first of these authors remarked tiiat nearly 

 all the liard 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 shown that 

 the detritus liad 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." Extending his observations to many 

 hundred jjlaces, he divided these scratches into what he calls normal 

 and side furrows, showing that in the latter there are frequent aber- 

 rations from the persistent courses of the former. Although he had 



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

 Phil. Mag. S. 3. Vol. 20. No. 1 3 1. Suppl. Julj/ 1842. 2 R 



