140 



ME. ALFRED HARKEE ON THE CARROCK FELL [May 1 895, 



horizontal surface of junction. This feature and the general simi- 

 larity of the several outcrops make it probable, as surmised by Ward, 

 that the three are parts of a single mass, which must then extend 

 from S.S.W. to N.1ST.E. for a distance of at least 4 miles. The most 

 southerly exposure is in Sinen Gill, a tributary of the Glenderaterra, 



on the west side of Saddleback ; 

 Fig. 2. the next and most extensive is in 



the Caldew valley, near Wiley Gill 

 and Burdell Gill ; the third, with 

 which we are more immediately 

 concerned, is lower down the 

 same valley, near the junction of 

 Grainsgill with the river Caldew. 

 Ward's fourth area, consisting of 

 ' poorly developed ' or ' bastard 

 granite,' at the head of Brand)' 

 Gill, I find to be an intrusion of 

 granophyre which has no con- 

 nexion with the Skiddaw granites. 

 The rock of the first and second 

 exposures calls for no special re- 

 mark. It is essentially a biotite- 

 granite, consisting of orthoclase, 

 oligoclase, quartz, and brown mica. 

 The last encloses numerous little 

 zircons, each surrounded by its 

 characteristic halo of intense pleo- 

 chroism, which is very conspicuous 

 even when the mica is much 

 decomposed. It must be remarked, however, that, in addition to 

 the magnesian mica, there are often scattered flakes of muscovite, 

 which are always subordinate and not constant enough to be regarded 

 as an essential constituent. The quartz is in part enclosed by the 

 felspar or, in places, roughly intergrown with it. 



Coming now to the third area of granite, and beginning with its 

 southern portion, as seen in the bed of the river, we notice a certain 

 difference. The rock is somewhat more acid, yielding 77*26 per 

 cent, of silica as compared with 75*223, 1 and its specific gravity has 

 diminished from 2*624 to 2-604. With this we find that white 



1 In addition to the other gentlemen named above, I am indebted to Mr. A. 

 Harden, of Owens College, Manchester, who has superintended the determina- 

 tion of several silica-percentages in his laboratory. One of these is indicated 

 by the letter M in the following list : — 



(i) Granite, White Gill : Silica 75-223 (Hughes), 

 (ii) Granite, bed of Caldew, 300 yards above junction with Grainsgill Beck : 



Silica 77-26 (S) ; sp. gr. 2-604. 

 (iii) Greisen, near foot of Brandy Gill: 



Silica 78-13 (M) ; sp. gr. 2 - 646, another specimen 2 - 669. 

 (iv) Greisen, eastern slope of Combe Height, 250 yards south of Grainsgill 



Lead-mine : Silica 80'36 (Spencer) ; sp. gr. 2 - 684. 

 (v) Greisen, small inlier in Grainsgill Beck, 400 yards above junction with 

 Brandy Gill : Sp. gr. 2-682. 



