Page:Quarterly Journal of the Geological Society of London, vol. 25.djvu/562

438 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [June 23, line the porphyry rises into the lofty chain of hills which separates Buttermere from Ennerdale, comprising Ling Comb, Red Pike, High Stile (2643 feet), and High Crag. From Scarf Gap the S.E. and S. boundaries of the syenitic mass are continued across the valley of the Liza (about 1-1/2 miles above Gillerthwaite), and thence to the south of Ennerdale Lake by Ling Mell, Iron Crag, and the Side, to the Revelin, all these hills being composed of the intrusive rock. All along these boundaries the syenite is overlain by the traps which form the base of the green slate series, the latter appearing to suffer no alteration near the line of junction.

As regards the mineral characters of this great intrusive mass, they are somewhat different in different localities. In the neighbourhood of Buttermere, and indeed throughout the greater part of its extent, it is merely a quartziferous porphyry, composed of a base of reddish felspar containing numerous crystals of white felspar, with specks of hornblende and grains of quartz disseminated through it. In other localities, however, as at the head of Ennerdale, quartz is present in considerable abundance; and the rock then assumes the characters of a true syenite.

III. The Felstone-porphyry of Carrock Fell.

This rock forms the summit and the northern spur of Carrock Fell, near Hesket-new-market, where its occurrence has been described by Prof. Harkness (Quart. Journ. Geol. Soc. vol. xix. p. 124). The area which it occupies is not of any very great extent, being about 1-1/2 mile from E. to W., and about a mile from N. to S. Throughout the greater part of its extent it is surrounded by trappean rocks, which belong to the series of the green slates and porphyries, and which do not appear to have undergone any alteration near the line of contact with the intrusive rock. Its eastern boundary extends from a farm called Stone Ends, near Mosedale, northwards as far as Carrock Beck. Its northern boundary runs up Carrock Beck, and is formed by the traps of West Fell and High Pike, though the junction is nowhere visible. On the south it is bounded by a singular crystalline rock which is seen near Mosedale, and forms a mass of great thickness. At its south-western corner, however, it becomes continuous with a mass of fine-grained granite, which is seen in Grainsgill Beck (Brandy Gill), close to the junction of this stream with the river Caldew. This fine-grained granite is surrounded by metamorphosed, gneissic Skiddaw Slates, which are seen almost in direct contact with it. It is, doubtless, as believed by Prof. Harkness, in turn continuous with the coarse granite which occurs higher up the valley of the Caldew, and which Prof. Sedgwick described under the name of "the Granite of Skiddaw Forest."

Admitting, as seems almost certain, that these three igneous masses are directly connected with one another, and pass into one another without a break, two facts are noticeable:—First, the strike of the igneous masses conforms to that of the stratified rocks amongst which they are situated. Thus the strike of the