Page:Geological Evidences of the Antiquity of Man.djvu/380

360 The annexed drawing represents one of the best known of train No. 6, being that marked n on the map, p. 357. According to our measurement it is fifty-two feet long by forty in width, its height above the drift in which it is partially buried being fifteen feet. At the distance of several yards occurs a smaller block, three or four feet in height, twenty feet long, and fourteen broad, composed of the same compact chloritic rock, and evidently a detached fragment from the bigger mass, to the lower and angular part of which it would fit on exactly. This erratic n has a regularly rounded top, worn and smoothed like the roches moutonnées before mentioned, but no part of the attrition can have occurred since it left its parent rock, the angles of the lower portion being quite sharp and unblunted.

From railway cuttings through the drift of the neighbourhood, and other artificial excavations, we may infer that the position of the block n, if seen in a vertical section, would be as represented in fig. 52. The deposit c in that section, p. 359, consists of sand, mud, gravel, and stones, for the most part unstratified, resembling the till or boulder clay of Europe. It varies in thickness from ten to fifty feet, being of greater depth in the valleys. The uppermost portion is occasionally, though rarely, stratified. Some few of the imbedded stones have flattened, polished, striated, and furrowed sides. They consist invariably, like the seven trains above mentioned, of kinds of rock confined to the region lying to the NW., none of them having come from any other quarter. Whenever the surface of the underlying rock has been exposed by the removal of the superficial detritus, a polished and furrowed surface is seen, like that underneath a glacier, the direction of the furrows being from NW. to SE., or corresponding to the course of the large erratics.

As all the blocks, instead of being dispersed from a centre, have been carried in one direction, and across the ridges, ,