Page:Quarterly Journal of the Geological Society of London, vol. 25.djvu/121

counterfort of the valley by a deep ravine. This crest is terminated by a rock of mica-schist, also separated from the right counterfort ; and upon this three isolated granitic blocks are perched. A stream of blocks thrown in line on the corresponding counterfort of the valley below the schistose rock shows the extreme termination of the glacier beyond the gorge. As the summits bounding the right side of the valley all consist of mica-schist, these granitic blocks cannot be regarded as having fallen from above. The left lateral moraine includes the blocks scattered about the hamlet of Costeilade : some of these project from the ground in cultivated fields ; and one, the last, is perched on a promontory of mica-schist, overhangs its pedestal, and resembles in form the head of a geological hammer. This is about 150 metres above the torrent. The peaks and crest about the left moraine are granitic, and considerable masses of rock have fallen from them ; but there is an interspace of about 250 metres between the foot of these and the highest blocks of the moraine. The terminal moraine is better marked than the lateral ones, and corresponds with the gorge which closes the " cirque " of Costeilade. The moraine forms a bar between the left counterfort of the valley and a low, rounded, isolated hill of schist which occupies the line of the water-way and drives the torrent towards the right. This isolated hill is remarkable. Rounded on the upper side, it is produced below into a crest of less elevation than itself, which bears only two small erratic blocks ; the hill itself on the contrary bears 32 large granitic blocks, all placed on the upper side, against which the vanished glacier impinged. No polished or striated rocks or scratched pebbles are to be met with ; but this is explained by the soft schistose nature of the rock forming the valley, which could neither have scratched the granite fragments, nor have retained any traces of polish or striation on its own surface.