154 VISCOUS THEORY OF GLACIER MOTION. [1846. 



the motion, by the force of the sun which has altogether wasted 

 away the side with the southern exposure, and by the copious 

 drippings of the melting ice and mild rain. No. 3 (which as 

 well as No. 2 is taken from a sketch on the spot, No; 1 being 

 done from recollection) shows what I have elsewhere called the 

 state of collapse of the glacier, which affords the most direct 

 possible evidence of its plastic condition ; for we there see, not 

 merely the prominences worn away and blunted by the heat of 

 summer, but subsiding into the hollows, the crevasses being 

 choked by the yielding of their sides, and the glacier again re- 

 sumes a traversable character, only that the plane surface 

 of spring is changed into irregular undulations preparatory 

 to a complete amalgamation of the whole glacier into one 

 mass.* 



The collapse is thus described in my Journal of 1842, writ- 

 ten at the time, and therefore more emphatic and unbiassed 

 than after my theoretical views had been matured and pub- 

 lished. " 1842, Sept. 16, Friday. The level (of the Mer de 

 Glace at the ' Angle ') has sunk since the 9th of August, nine 

 feet 8J inches. The effect of this immense fall is abundantly 

 evident in this part of the glacier. On my first visit this time 

 (i. e., after an absence of a month), on the 10th, I was quite 

 struck with its shrunk appearance, as I was to-day with the col- 

 lapsed state of the crevasses. There cannot be a question but 

 that the glacier had subsided bodily into its bed, and that the 

 semifused pliancy of its materials causes them to recover a uni- 

 form and lower level. The crevasses are much less deep than 

 in July arid August, as at that time they were larger and more 

 numerous than in June. They are collapsed and (opposite 

 Trelaporte) almost soldered up ; the edges all rounded and 

 melted by the sun's heat." The phenomena here described, " the 

 shrunk appearance," "the semifused pliancy" "the soldered 

 crevasses," " the rounded edges," convey to the attentive spec- 

 tator an intuitive conviction of the plasticity of ice at the thaw- 



* See Travels, p. 174; and Fourth Letter on Glaciers [pages 27 and 28.] 



