83 



"soil, with abundant sorrel, willow, saxifrages, and grasses, 

 " instead of hard limestone and gravel plains." 



Lieut.-Col. Godwin Austen, apropos of this subject (see Q.J.G.S. 

 xl. 612) and of our own neighbourhood, speaks of the formation 

 of frozen snow beds on the higher grounds, " such as those 

 " patches of ice many square acres in extent that can be seen at 

 " the present day on the wide level plateau of the Chang 

 " Chingmo in Thibet, that is to say, solid ice not more than 

 " twenty feet thick, with a flat but much broken surface, and with 

 " a wall-like margin in most places. These I noticed lasted 

 " until the winter snows began again, and in warm summers they 

 " may almost disappear." . . . . " Such snow," he continues, 

 " and such frozen snow beds, would have quite sufficient force 

 " to act on the surface of the country, wearing it down to the 

 " even beautiful curves it now presents." 



Secondly, there is another means of explaining the formation of 

 underplight and trail. 



That of the intermittent flowing, by its own weight, of a soil under- 

 going a thaw or regelation {regelare, to thaw), that is, in a 

 viscous state, or one of unequal coherence. 



In Arctic lands where the subsoil is frozen permanently, the surface 

 soil is thawed for a certain depth only. In the act of freezing 

 again, the expansion of the ice separates the fragments and layers 

 of rock ; on, the liquefactioa of this ice the small fissures are 

 occupied by a larger quantity of water than before. The widening' 

 of the minute fissures in the rock having been increased by the 

 ice, permits the water of the thawing snow to fill the fissures 

 instead of running off until the soil is almost fluid. In the 

 valleys of the Aniui, where the vegetation is comparatively rich, 

 Wrangell mentions that " the snow appears to melt only to form 

 " fresh ice beneath the covering of mould," not flowing off as 

 water. (Wrangell trans. : by Sabine p. 51). 



When the surface is bared the sun converts the whole to mush 

 or sludge, which partially flows from the upper ground to the 

 lower, leaving the rock nearer to the surface ready for the next 

 thaw to attack it. 



Sir E. Belcher says that " Buckingham Island is belted from the 

 " first base of this elevated range (200ft. above the sea) by a low 

 " marshy slope of frozen mud, thickly covered with tufts of 

 "grass. This mud is the result of the ddbris during the summer 

 " thaw, which appears to lose itself in the sea, distant from the 

 " elevated land about a quarter of a mile." Having reached the 

 "highest mound "of this elevation, he continues, " At the time 



