§ 17. The way in which these curves are produced cannot, however, be guessed at until we examine the junction more closely. Ascending about five hundred feet above the cabin of the Montanvert, the opposite crest of the Bouchard, from a to c, [Plate 33], is seen more in front, expanded into the jagged line, a to c, [Plate 34], and the beds, with their fractures, are now seen clearly throughout the mass, namely:
1st. (See references on plate). The true gneiss beds dipping down in the direction G H, the point H being the same as h in [Plate 33]. These are the beds so notable for their accurate straightness and parallelism.
2nd. The smooth fractures which in the middle of the etching seem to divide the column of rock into a kind of brickwork. They are very neat and sharp, running nearly at right angles with the true beds.[72]
3rd. The curved fractures of the aiguilles (seen first under the letter b, and seeming to push outwards against the gneiss beds[73]) continuing through c and the spur below.
4th. An irregular cleavage, something like that of starch, showing itself in broken vertical lines.
5th. Writhing lines, cut by water. These have the greatest possible influence on the aspect of the precipice: they are not merely caused by torrents, but by falls of winter snow, and stones from the glacier moraines, so that the cliff being continually worn away at the foot of it, is wrought into a great amphitheatre, of which the receding sweep continually varies the apparent steepness of the crest, as already explained. I believe in ancient times the great Glacier des Bois itself used to fill this amphitheatre, and break right up against the base of the Bouchard.
6th. Curvatures worn by water over the back of the crest towards the valley, in the direction g i.
7th. A tendency (which I do not understand) to form horizontal masses at the levels k and l.[74]
| Fig. 61. |