MOTION OF GLACIER DE LÉCHAUD.
Seventh Line: K K' upon Sketch.
| Stake | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
| Inches | 5 | 8 | 10 | 9 | 9 | 8 | 6 | 9 | 7 | 6 |
199. Here our conjecture is still further verified, the rate of motion being even less than that of the Glacier du Géant.
[§ 28.] Motion of Top and Bottom of Glacier.
200. We have here the most ample and varied evidence that the sides of a glacier, like those of a river, are retarded by friction against its boundaries. But the likeness does not end here. The motion of a river is retarded by the friction against its bed. Two observers, viz. Prof. Forbes and M. Charles Martins, concur in showing the same to be the case with a glacier. The observations of both have been objected to; hence it is all the more incumbent on us to seek for decisive evidence.
201. At the Tacul (near the point a upon the sketch plan, p. 83) a wall of ice about 150 feet high has already attracted our attention. Bending round to join the Léchaud the Glacier du Géant is here drawn away from the mountain side, and exposes a fine section. We try to measure it top, bottom, and middle, and are defeated twice over. We try it a third time and succeed. A stake is fixed at the summit of the ice-precipice, another at 4 feet from the bottom, and a third at 35 feet above the bottom. These lower stakes are fixed at some risk of boulders falling upon us from above; but by skill and caution we succeed in measuring the motions of all three. For 24 hours the motions are:—
| Top stake | 6 | inches. | |
| Middle stake | 4 | ½ | " |
| Bottom stake | 2 | ⅔ | " |
202. The retarding influence of the bed of the glacier is reduced to demonstration by these measurements. The bottom does not move with half the velocity of the surface.
[§ 29.] Lateral Compression of a Glacier.