[Footnote 239: Mr. Dakyns has expressed his belief that the volcanic group lies unconformably on the Skiddaw Slate (_Geol. Mag._ 1869, pp. 56, 116), and Professor Nicholson has formed the same opinion (_op. cit._ pp. 105, 167; _Proc. Geol. Assoc._ vol. iii. p. 106). Mr. Goodchild, however, has shown that in the Cross Fell inlier the oldest tuffs are interstratified with the Skiddaw Slates (_Proc. Geol. Assoc._ vol. xi. (1889), p. 261). Mr. Ward in mapping the district inserted a complex series of faults along the junction-line between the volcanic series and the Skiddaw Slates. When I went over the ground with him some years before his death I discussed this boundary-line with him and could not adopt his view that it was so dislocated. More recent re-examination has confirmed me in my dissent. A large number of the faults inserted on the Geological Survey map to separate the Skiddaw Slates from the Borrowdale volcanic series cannot be proved, and probably do not exist. Others may be of the nature of "thrust-planes." But see Mr. Ward's explanation of his views, _op. cit._ p. 48.] The materials that form this enormous volcanic pile consist entirely of lavas and ashes. No intercalations of ordinary sedimentary material have been met with in it, save at the bottom and at the top. The lower lavas, well seen among the hills to the south of Keswick, were shown by Mr. Ward to be intermediate between felsites and dolerites in regard to their silica percentage, and he proposed for them the name of felsi-dolerites. They are comprised in the group of the andesites or "porphyrites." From the analyses published by Mr. Ward, the amount of silica appears to range up to about 60 per cent.[240] They are usually close-grained, dull dark-grey to black rocks, breaking, where fresh, with a splintery or conchoidal fracture, showing a few minute striated felspars, apt to weather with a pale-brown or yellowish-grey crust, and sometimes strongly vesicular or amygdaloidal. They present many external resemblances to some of the "porphyrites" or altered andesites of the Lower Old Red Sandstone of Scotland. A microscopic examination of specimens collected by Dr. Hatch and myself from the hills to the south of Keswick showed the rocks to be true andesites, composed of a multitude of slender laths (sometimes large porphyritic crystals) of felspar with a brownish glassy groundmass, and with some chloritic material probably representing augite, but with no trace of quartz.[241] [Footnote 240: _Quart. Journ. Geol. Soc._ vol. xxxi. (1875) p. 408, vol. xxxii. (1876) p. 24. Geology of Northern Part of Lake District (_Mem. Geol. Survey_), p. 22. In a subsequent paper the more basic lavas of Eycott Hill are compared with dolerites (_Monthly Microscopical Journ._ 1877, p. 246).]