It was at the base of the Talèfre cascade that the explanation of these curious seams presented itself to me. In one of my earliest visits to this portion of the glacier I was struck by a singular disposition of the blue veins on the vertical wall of a crevasse. [Fig. 56] will illustrate what I saw. The veins, within a short distance, dipped backward and forward, like the junctions of stones used to turn an arch. In some cases I found this variation of the structure so great as to pass in a short distance from the vertical to the horizontal, as shown in [Fig. 57].
VARIATIONS IN "DIP" OF STRUCTURE.
Further examination taught me that the glacier here is crumpled in a most singular manner; doubtless by the great pressure to which it is exposed. The following illustration will convey a notion of its aspect: Let one hand be laid flat upon a table, palm downwards, and let the fingers be bent until the space between the first joint and the ends of the fingers is vertical; one of the crumples to which I refer will then be represented. The ice seems bent like the fingers, and the crumples of the glacier are cut by crevasses, which are accurately typified by the spaces between the fingers. Let the second hand now be placed upon the first, as the latter is upon the table, so that the tops of the bent fingers of the second hand shall rest upon the roots of the first: two crumples would thus be formed; a series of such protuberances, with steep fronts, follow each other from the base of the Talèfre cascade for some distance downwards.
On Saturday the 1st of August I ascended these rounded terraces in succession, and observed among them an extremely remarkable disposition of the structure. [Fig. 58] is a section of a series of three of the crumples, on which the shading lines represent the direction of the blue veins. At the base of each protuberance I found a seam of white ice wedged firmly into the glacier, and each of the seams marked a place of dislocation of the veins. The white seams thinned off gradually, and finally vanished where the violent crumpling of the ice disappeared. In [Fig. 59] I have sketched the wall of a crevasse, which represents what may be regarded as the incipient crumpling. The undulating line shows the contour of the surface, and the shading lines the veins. It will be observed that the direction of the veins yields in conformity with the undulation of the surface; and an augmentation of the effect would evidently result in the crumples shown in [Fig. 58]. The appearance of the white seams at those places where a dislocation occurred was, as far as I could observe, invariable; but in a few instances the seams were observed upon the platforms of the terraces, and also upon their slopes. The width of a seam was very irregular, varying from a few inches at some places to three or four feet at others.
CRUMPLES OF THE TALÈFRE.
MOULDS OF WHITE ICE-SEAMS.
On the 3rd of August I was again at the base of the Talèfre cascade, and observed a fact the significance of which had previously escaped me. The rills which ran down the ice-slopes collected at the base of each protuberance into a stream, which, at the time of my visit, had hollowed out for itself a deep channel in the ice. At some places the stream widened, at others its banks of ice approached each other, and rapids were produced; in fact, the channels of such streams appeared to be the exact moulds of the seams of white ice.