No. of stake. Inches. East 1 moved 19-1/2 2 " 22-3/4 3 " 28-3/4 4 " 30-1/4 5 " 33-3/4 6 " 28-1/4 7 moved 24-1/2 8 " 25 9 " 25 10 " 18 11 " ... 12 " 8-1/2 West.
The numbering of the stakes along this line commenced from the Chapeau-side of the glacier, and the retardation of that side is now manifest enough; the motion gradually augmenting from 19-1/2 to 33-1/2 inches. But, comparing the velocity of the two extreme stakes, we find that the retardation of stake 12 is much greater than that of stake 1. Stake 5, moreover, which moved with the _maximum_ velocity, was not upon the centre of the glacier, but much nearer to the eastern than to the western side.
[Sidenote: A NEW PECULIARITY OF GLACIER MOTION.]
It was thus placed beyond doubt that the point of maximum motion of the Mer de Glace, at the place referred to, is not the centre of the glacier. But, to make assurance doubly sure, I examined the comparative motion along three other lines, and found in all the same undeviating result.
This result is not only unexpected, but is quite at variance with the opinions hitherto held regarding the motion of the Mer de Glace. The reader knows that the trunk-stream is composed of three great tributaries from the Géant, the Léchaud, and the Talèfre. The Glacier du Géant fills more than half of the trunk-valley, and the junction between it and its neighbours is plainly marked by the dirt upon the surface of the latter. In fact four medial moraines are crowded together on the eastern side of the glacier, and before reaching the Montanvert they have strewn their débris quite over the adjacent ice. A distinct limit is thus formed between the clean Glacier du Géant and the other dirty tributaries of the trunk-stream.
Now the eastern side of the Mer de Glace is observed on the whole to be much more fiercely torn than the western side, and this excessive crevassing has been referred to _the swifter motion of the Glacier du Géant_. It has been thought that, like a powerful river, this glacier drags its more sluggish neighbours after it, and thus tears them in the manner observed. But the measurement of the foregoing three lines shows that this cannot be the true cause of the crevassing. In each case the stakes which moved quickest _lay upon the dirty portion of the trunk-stream_, far to the east of the line of junction of the Glacier du Géant, which in fact moved slowest of all.
