264: TIME CONSIDEEATIONS 



decomposition might be expected, such has not as yet been 

 proven to actually take place, and indeed many facts tend to 

 prove the impression quite erroneous. Lack of decomposition 

 products in high latitudes is frequently due to glaciation or 

 erosion by other means. Whitney,^ Irving,^ Chamberlain, and 

 Salisbury^ have shown the presence of residual clays of all 

 thicknesses up to 25 feet in the driftless area of "Wisconsin, 

 and Chamberlain has described"* limited areas of strongly decom- 

 posed gneiss in the non-glaciated areas of Greenland. 



Moreover, we have no actual proof that the action of frost 

 is, on the whole, protective, as is stated by Branner.^ It must 

 be remembered that frost, excepting in the extreme north, 

 penetrates to but a slight depth, and while it undoubtedly puts 

 a temporary stop to chemical action on the immediate surface, 

 it remains yet to be shown that the mechanical disruption that 

 ensues, as described in previous pages, is not as efficacious 

 as would have been the chemical agencies alone, had they been 

 permitted to continue their work. Through bringing about a 

 finely fissile or pulverulent structure, whereby a vastly greater 

 amount of surface becomes exposed, frost prepares the way for 

 chemical action at a thousand-fold more rapid rate than could 

 otherwise have been possible. If, further, as the writer has 

 elsewhere at least suggested,^ hydration is the most potent 

 factor in rock decomposition, the process can go on uninter- 

 ruptedly below the level of freezing. 



Professor H. P. Gushing has described^ the argillites in the 

 vicinity of Glacial Bay, Alaska, as in a condition of great dis- 

 integration, wholly through the action of frost. *^ Disintegra- 

 tion," he says, 'Hakes place with amazing rapidity, as shown 

 by the enormous piles of morainic matter furnished to the tribu- 

 taries of Muir Glacier, whose valleys are adjoined by mountains 

 of argillite, and by the massive talus heaps that are rapidly 

 accumulating at the bases of other mountains made up of the 

 same material." In a private communication to the present 



^Eep. Geol. Survey of Wisconsin, 1861. 

 ^ Trans. Wisconsin Acacl. of Science, Vol. HI, 1875. 

 * Ann. Eep. U. S. Geol. Survey, 1884-85, p. 254, 

 *BulL Geol. Soe. of America, Yol. JI, 1895, p. 218. 

 '^ Bull. Geol. Soe. of America, Vol. VII, 1896, p. 282. 

 «Bull. Geol. Soe. of America, Vol. VI, 1895, p. 331. 

 ^ Trans. N. Y. Academy of Science, Vol. XV, 1895. 



