described in § 7. The highest points of the rocks are most affected, while the sides of depressions escape wholly, or partially, according as they are unopposed or opposed, to the direction of the motion of the glacier. Eminences are entirely removed in course of time", and their positions, and those of cracks or depressions, are only indicated by faintly-marked convexities and concavities (Fig. 4). These may at length disappear, and large areas of rock may be reduced to plane surfaces.
Such surfaces are common in Greenland, in close proximity to, and extending underneath, existing glaciers. I propose to call them roches nivelées, to distinguish them from roches moutonnées.[1]
§ 9. Striations are frequently produced on rocks by the passage of glaciers (see illustration on p. 141). They are caused by foreign matter in the bottoms of the glaciers, fixed in the ice, or rolling or sliding between it and the rocks. This foreign matter is partly made up of fragments which have been removed from the rock-bed by the action of the glacier, and partly from rocks which have fallen on to the surface of the glacier, and which have subsequently tumbled into crevasses, or otherwise worked their way down.[2]
Generally speaking, striations are common upon rocks which are only 'moutonnées,' but they are rarer, or entirely wanting, upon
- ↑ De Saussure was the author of the term roches moutonnées, and he gave (§ 1061) the following reason for its adoption:—"Farther off, behind the village of Juviana
or Envionne, rocks are seen having the shape which I call moutonnée. . . The hillocks (montagnes) to which I apply this expression, are composed of a group of rounded prominences (têtes arrondies). . . These contiguous and frequent domes (rondeurs) give, as a whole, the impression of a well-furnished fleece, or one of those wigs which are also called moutonnées."
The term was an appropriate one, applied as De Saussure used it, but it is unmeaning when applied to the more perfectly glaciated, levelled surfaces.
- ↑ "One who is familiar with the track of this mighty engine will recognise at once where the large boulders have hollowed out their deeper furrows, where small pebbles have drawn their finer marks, where the stones with angular edges have left their sharp scratches, where sand and gravel have rubbed and smoothed the rocky surface, and left it bright and polished. . . These marks are not to be mistaken by any one who has carefully observed them; the scratches, furrows, grooves, are
