Page:Quarterly Journal of the Geological Society of London, vol. 26.djvu/900

From Wikisource
Jump to navigation Jump to search
This page needs to be proofread.

Geikie* as more or less solitary mounds of stratified gravel, running in a " sinuous line, from a few yards to several miles in length, averaging perhaps from 50 to 60 feet in height, and rising abruptly from the ground into a narrow crest." Some of the pebbles of the gravel of the Kames described by Mr. Geikie he found to be scratched by ice. Possibly some of the Scotch Kames may be of the Middle-drift age ; but, at the same time, even if this be the case, there can be no reason to suppose that ice, on a limited scale, may not have been present during the period of the formation of the Kames, as well as of the Middle-Drift sand and gravel, especially as there can be little doubt that glaciers lingered in the deep valleys of the Cumberland mountains long after the elevation that lifted the Kames high above the sea.

Moraines. — During a few days' leave of absence, spent in the lake-district of Westmoreland and Cumberland, I observed that all the great lakes I visited (Windermere, Grasmere, Thirlmere, Ulleswater, Brothers' water, and Elterwater) lay in true " rock-basins," the rock bottom sloping inwards in all directions, with a gradual inclination at first, and then a sudden deep plunge to the bottom of the lake. The lakes run in chains, like extended river-courses, through deep gorges of rock, the sides of which are scored with glacial markings ; these I observed near the head of the lake (with the help of a glass) at the bottom of Windermere itself. Roches moutonnes are found at the foot of most of the lakes, notably at Grasmere, where the river has cut for itself a sort of groove, or slot, through the rock. Everywhere the rivers merely carry away the surface- or overflow- water of the lakes, the rock-surface under the water being even steeper on the outlet side than on the inlet, partly perhaps from the deposition of alluvium, but mainly, one cannot help considering, by the rock being worn into a slope by the gradual passing over, onwards and downwards, of the glaciers which must once have filled those gorges, while the enormous pressure from behind, tending to cause an upward movement, would cause the steep and cliff -like declivity of the lower ends of the lake- depressions. At the mouths of nearly all the lateral valleys running into the gorges patches of moraine matter occur, as well as at the entrance of the great Windermere gorge itself, descending as low as to 150 feet above the sea. In the Furness district, immediately to the south, the three drifts of Mr. Hull occur, the Upper Boulder-clay reaching elevations of nearly 300 feet at Hawcoat, near Barrow : and as it occurs at elevations of far greater height in the country to the south of Morecambe Bay, it would appear nearly certain that it, as well as the Middle Drift and Lower Boulder- clay, is absent in the lake-district, having been scooped out by the glaciers which occupied these valleys at the close of the Glacial epoch. I abstain from giving further details of this district, partly because I have published some notes upon it in the ' Geological Magazine,' partly because Mr. Hull has done so, in a paper in the

  • " On the Phenomena of the Glacial-drift of Scotland," Trans. Geol. Soc. of

Glasgow, vol. i. part ii. 1863, p. 112.