360 MERRILL — DISINTEGRATION AND DECOMPOSITION OF DIABASE. 



If, further, as I have elsewhere at least suggested,''^ hydration is a 

 most i:)otent factor in rock disintegration, the process can go on uninter- 

 ruptedly below the level of freezing. 



The extremely energetic manner in which frost action may manifest 

 itself under favorable conditions is -well set forth in the following mem- 

 oranda made b}^ Dr L. Stejneger during his sta}^ at the Commander 

 islands in Bering sea. He saj^s : 



"In September, 1882, I visited Tolstoi Mys, a precipitous cliff near the south- 

 eastern extremity of Bering island. At the foot of it I found larj^e masses of rock 

 and stone which had evidently fallen down during the year. j\Iost of them were 

 considerably more than six feet in diameter, and showed no trace of disintegra- 

 tion. The following spring, April, LS83, when I visited the place I found that the 

 rocks had split up into innumeraljle fragments, cube-shaped, sharp-edged and of a 

 very uniform size, about two inches. They had not yet fallen to pieces, the rocks 

 still retaining their original shape. 



" I may remark, however, that the weather was still freezing when I was there. 

 The winter was not one of great severity, and several thawing spells broke its 

 continuity. 



"These cubic fragments did not seem to split up any further, for everywhere on 

 the islands where the rock consisted of the coarse sandstone, as in this place, the 

 talus consisted of these sharp-edged stones." 



Professor H. P. Gushing has also remarked the extensive disintegra- 

 tion of the argillites at Glacier bay, Alaska. He says : 



" Disintegration takes place with amazing rai)idity, as shown by the enormous 

 piles of morainic matter furnished to the tributaries of Muir glacier, whose valleys 

 are adjoined by mountains of argillite and by the massive talus heaps that are 

 ra])idly accumulating at the bases of other mountains, made up of the same ma- 

 terial.'' t 



This breaking down is largely physical and due to frost action, as de- 

 scribed in the notes of Dr Stejneger above. In a private connnunication 

 to the writer Professor Gushing further states that the diabase dikes of 

 the region are fully as much decomposed as those of the Adirondacks, and 

 that the boulders of eruptive rocks in the moraines are also far gone in 

 decomposition. 



In temperate regions we have further to consider the possible increased 

 amounts of atmos[)heric gases brought down by snowfalls over those 

 brought by rain. The snow flakes in falling so comj^letely fill the air as 

 to rob it of a larger proportion of the gases than would a corresponding 

 amount of precipitation in the form of rain. Further, the snow in melt- 

 ing slowly away affords the water better facilities for soaking into the 



* Bull. Geol. Soe. Am., vol. C, p. 331. 



t Trans. New York Acad, of Sciences, vol. xv, 1895, p. 25. 



