Page:A Treatise on Geology, volume 1.djvu/145

 CHAP. VI. gneiss: and declining to the south-east from an axis of elevation which ranges N.E. and S.W. The dip, judged of by appearance on Derwent Water, in Borrowdale and Grasmere, appears to be considerable, yet not very steep: probably not exceeding, on an average of many miles, 10°.



The above diagram represents the whole series of rocks of this system, in their real order of superposition. The following reference will be sufficient to aid the reader's conception.

In Wales, also, these very ancient strata may be traced on the west of Snowdonia and between Cader Idris and Moel Siabod. Mr Jukes and Mr. Selwyn have presented a section of the latter district (Geological Proceedings, 1848.). The former is familiar to English geologists, in consequence of the interest inspired by the well known previous researches of Sedgvvick; and as the whole of Wales has at length been coloured on the Ordnance maps by Sir H. De la Beche, Mr. Ramsay, and their friends, and illustrated by measured sections, the data for reasoning are gradually growing complete. The section from Snowdonia westward to the Menai is, on many accounts, one cf the finest in Wales. Commencing in Anglesea, we have undulations of micaceous and chloride schists with quartz rocks, apparently the