Page:Transactions of the Geological Society, 1st series, vol. 1.djvu/221

 This bed is very distinctly stratified; it rises N.W. at an angle of about 55° where it rests on the Wrekin and Caer Caradoc, but in the intermediate space at an angle of about 40°.

Beneath the quartz-grit lies a very extensive bed of claystone or compact felspar (for it presents the characters of both these minerals in different places, and even occasionally passes into jasper). Sometimes it is very distinctly slaty and stratified, which is particularly the case with the lowest part of the bed, which rests on greenstone and amygdaloid, and occasionally exerts a pretty strong action on the magnetic needle. The craggy eastern side, both of the Wrekin and of Caer Caradoc, consists of the slaty variety of this rock in nearly vertical strata; at the Arcal hill, it appears in the state of compact felspar, covered to a considerable thickness by a mixture of fragments of greenstone and felspar, more or less decomposing into a tenacious clay; it is nearly pure compact felspar at Wrockardine hill, the sides of which are covered by a soft brownish-red very fine-grained sandstone, probably originating from the decomposition of the felspar.

Under the claystone occurs an unstratified trap-formation which constitutes the great mass of the Wrekin, the Lawley, Caer Caradoc, Ragleath and Hope Bowdler hills, the various component parts of which will be best understood by arranging them under the general heads of felspar rocks and greenstone rocks.


 * 1. Felspar rocks.

The basis of all these is a claystone or compact felspar, of a colour between flesh and brick-red, and they serve as the immediate support of the superincumbent claystone. None of them affect the magnetic needle.

The variety which is most prevalent on the top of Caer Caradoc is a cellular claystone, the cavities of which vary in size from that of a small almond to a pin's head, and are all of them, especially the