178 THE PEINCIPLES INVOLVED IN ROCK-WEATHER I NG 



whicli, in extreme cases, are so abundant as to make up, aeeord- 

 ing to Sorby, at least 5% of the whole volume of the mineral. 



That the passage of this included moisture from the liquid 

 to the solid state, must be attended with results disastrous to 

 the stone is self-evident, though the rate of disintegration may 

 be so slow under favorable circumstances as to be scarce notice- 

 able. Freezing of the absorbed water is one of the most fruit- 

 ful sources of disintegration in stones conjSned in the walls of 

 a building, and even in the quarry bed it is by no means uncom- 

 mon to have stone so injured as to render it worthless. How- 

 ever slight may be the effects of a single freezing, constant 

 repetition of the process cannot fail to open up new rifts, and 

 still further widen those already in existence, allowing further 

 penetration of water to freeze in its turn and to exert a chemical 

 action as well. So year in and year out, through winter's cold 

 and summer's heat, the work goes on until the massive rock 

 becomes loose sand to be caught up by winds or temporary 

 rivulets and spread broadcast over the land. In some instances, 

 it may be, the rock is of sufficiently uniform texture to be af- 

 fected in all its mass alike. More commonly, however, it is 

 traversed by veins, joints, or other lines of weakness along 

 which the rifting power is first made manifest, as in the illustra- 

 tion. (PL 19.) Naturally disintegration of this kind is con- 

 fined to frigid and temperate latitudes. As bearing upon the 

 extreme rapidity with which such disintegration may take place, 

 the following is quoted from a letter of Dr. L. Stejneger, of the 

 United States National Museum, who passed several months 

 among the islands of Bering Sea. 



''In September, 1882, I visited Tolstoi Mys, a precipitous 

 cliff near the southeastern extremity of Bering Island. At the 

 foot of it I found large masses of rock and stone which had 

 evidently fallen down during the year. Most of them were 

 considerably more than six feet in diameter, and showed no 

 trace of disintegration. The following spring, April, 1883, 

 when I revisited the place, I found that the rocks had split up 

 into innumerable 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 



