218 Professor Forbes on the Leading Phenomena of Glaciers. 



which I had previously suspected, although opposed to the re- 

 ceived opinions, — that the glacier moves with considerable ve- 

 locity even in winter. By going to the spot with Balmat, and 

 verifying the marks which he had from time to time made, I 

 ascertained that his measurements, if not absolutely correct, 

 did not admit of being materially improved, owing to the great 

 size and repeated turning over of the block in question. His 

 measurements between October 1842 and June 1843, have 

 been published in the volume already cited. I had the morti- 

 fication, however, to find, on the 11th September 1843, when I 

 visited the block, that though still upon the ice, it had got shoved 

 so near the moraine of the glacier near an angle of its course, 

 as to be well nigh stranded ; and that, in fact, since Balmat's 

 last mark in June, its motion had been scarcely perceptible. 

 It farther appeared, that the part of the glacier with which it 

 had recently been moving, was so crevassed and steep, that 

 the vast block must have rolled and tossed about, or even 

 been precipitated occasionally forwards by the failure of the 

 ice beneath it on the steep, in a way which amply accounts for 

 any want of regularity in its winter progress, as indicated by 

 Balmat' s measurements. It therefore became the more inte- 

 resting and important to determine with care, the motion of a 

 point of the glacier removed from the accidental local influ- 

 ence of the sides and irregularities of the surface, in order to 

 compare the mean annual motion with the summer motion of 

 the ice. The " Pierre platte" was, in every way, an unexcep- 

 tionable landmark ; and I resolved to cross the Mer de Glace 

 for the purpose of accomplishing it — an exertion which I 

 should hardly have ventured for a less interesting result. In 

 the course of this walk, which was fraught with interest to 

 me, as enabling me to compare the existing condition of a 

 glacier with the appearances which had been so familiar to me 

 just twelve months before, I found the state of the ice just 

 such as might be expected after a very severe and snowy 

 winter, and a very cold and late summer. The glacier oppo- 

 site the '• angle" (station A), had now a much higher level than 

 it had at the same time in 1842 ; evidently, therefore, it had, 

 during the winter, regained its usual volume ; and then, dur- 

 ing the ensuing summer, it had wasted less than it had done 

 during the summer before. The glacier also bore other 



