Page:Quarterly Journal of the Geological Society of London, vol. 26.djvu/724

 course which the blocks have taken in their passage over the high ground of Stainmoor.

The area over which the granite blocks of Wastdale Crag have been dispersed is indicated in the map (Pl. XXXV.) by the portion marked with broken lines.

With reference to the relation which the blocks of Wastdale-Crag granite bear to the Boulder-clays of Westmoreland, it would seem, from the position of the former, that they have been dispersed after the deposition of the latter. The granite blocks occur in great profusion on the surface in the country between Wastdale Crag and the valley of the Eden. They do not make their appearance in the Boulder-clay. They are, however, occasionally met with in a clay which overlies the boulder-deposits ; but in this clay none of the characteristic scratched blocks of the Boulder-clay proper are found. This clay, overlying the Boulder-clay, is of local occurrence. It is seen at Gaythorn tile-works in Gaythorn plain, about five miles E.N.E. of Wastdale Crag. Here it has its origin from some shale- beds which occur in the carboniferous formation at this spot, and it is seen resting upon well-marked Boulder-clay.

In the vale of the Eden the Boulder-clay is largely developed, and good sections of it are exhibited in the cuttings of the Eden-valley branch of the South Durham railway. In no instance do any of these sections afford traces of blocks of Wastdale-Crag granite ; and although boulders abound in this clay, they have been, for the most part, derived from the Carboniferous formation. Occasional porphyritic blocks, such as might have been derived from the lake-country, and fragments of Coniston flags, which may have come from the Ravenstonedale district, are also seen in the Boulder- clays of the valley of the Eden.

Near the N.W. portion of the area of distribution of the Wastdale-Crag blocks, fragments of these become very rare; but masses of Lower Silurian porphyries and slates are common on the surface. Masses of granite also make their appearance ; but this granite has a very different aspect from that of Wastdale Crag, and these blocks seem to have come from Criffel, a granite hill on the S.E. side of the Stewartry of Kirkcudbright. As we proceed north from the area of the distribution of the Wastdale-Crag granite, the blocks from Criffel become more abundant. This Criffel granite occurs, not only in the form of blocks on the surface, but is found also in the Boulder-clays. It can be seen in this position at Brougham brick-works, about two miles W.N.W. of Cliburn, which is somewhat beyond the limits of the distribution of the Wastdale-Crag blocks. The Criffel granite blocks are also common in the Boulder-clays of the vale of the Eden, in Cumberland. They are likewise found in great abundance among the Eskar mounds near the road between Penrith and Long Wathby ; and here they have been derived from the Boulder-clay upon which these Eskar drifts repose.

Judging from the mode of occurrence of the Criffel granite blocks, as compared with those of Wastdale Crag, it would appear that the former had, to a large extent, been distributed before the latter;