Page:Quarterly Journal of the Geological Society of London, vol. 26.djvu/716

 by Professor Phillips, who has described the direction which these blocks have taken during the period of their dispersion ; who also mentions the occurrence of these blocks on Stainmoor, a pass in the Pennine chain, and their having travelled over some of the hills and valleys of Westmoreland, South Durham, and Yorkshire*.

Wastdale Crag, from which these blocks have been derived, is a low rounded hill, a little more than four miles N.W. of Tebay station, on the Lancaster and Carlisle railway. It is composed wholly of porphyritic granite, which, on the western side of the granitic area, attains an elevation of about 1600 feet above the level of the sea.

This area of porphyritic granite is flanked, on the western side, by ashes and porphyries, which belong to the Bala age ; and these ashes and porphyries on this side, immediately adjoining the granite, attain to a greater elevation than the granite, rising to a height of 1853 feet in the summit of Wastdale Pike ; and a little further westward some of the hill- tops are somewhat higher.

The granitic area of Wastdale Crag has a somewhat irregular outline. Its greatest breadth is from E.S.E. to W.N.W., being about two miles across. In a north and south direction, the greatest length which it attains is about 1-2/5 mile†.

The country for about 1-1/4 mile east of Wastdale Crag is somewhat open and flat, with an elevation of about 1100 feet above the sea.

A short distance further east it sinks down to about 800 feet, so that the highest point of the granite is about 800 feet above the country immediately east of the Crag.

The district east of Wastdale Crag is the area over which the great mass of the granite blocks has been dispersed; but this dispersion is not confined to an eastern course. Large blocks of granite are very abundant in the town of Shap, and they can also be seen in the walls for a distance of about half a mile west of Shap, on the road to Shap Abbey‡. Their position here is about three miles due north of Wastdale Crag, and the blocks, as contrasted with such as are seen in Shap itself, are of a comparatively small size. There are, however, some large blocks of rocks in the fields between Shap and Shap Abbey, which have received the name of " Thunder-stones." These are not granite masses, but consist of green porphyries, which have come from the high ground on the west side of the river Lowther.

The country which lies east and north-east of Shap exhibits great quantities of Wastdale-Crag boulders. In a N.N.E. direction, they can be traced six miles from Shap, being seen in the walls and


 * Geol. of Yorkshire, vol. ii. p. 162.

† I am indebted to the kindness of W. T. Aveline, Esq., of the Geol. Survey, for furnishing me with a tracing of the granite area of Wastdale Crag.

‡ In many localities where Wastdale-Crag blocks and other large boulders occur, they have been removed from their original positions in consequence of agricultural improvements. They have been used extensively for walling-purposes, and, in many spots, large blocks of these rocks have been made use of for basement courses of houses and farm-buildings.