552 Alfred Harker — VarioUtic Rocks on Carrock Fell. 



about the summit of Carrick Fell. They have a dark compact 

 appearance, with a colour varying from greenish-gray to brownish- 

 gra3\ There is often a strong banding parallel to the walls of the 

 vein, while a certain crumpling of the brittle rock has sometimes 

 given rise to a kind of cross-jointing resembling a rough cleavage- 

 structure. 



A slice was prepared from one of these veins, about 60 yards 

 east of the summit, the specific gravity of the rock being 2'846. 

 The slice [1754] is considerably obscured by secondary changes. 

 Where the structure is most regular, it shows dull round or ovoid 

 spots, averaging O'Ol inch in diameter, set rather close together 

 with clearer interspaces of a light brownish-green tint. This greeu 

 substance might be taken at first glance for an altered glass ; but 

 when examined with polarised light it is seen to be doubly 

 refracting, and the manner in which dark rays sweep across it, 

 when the stage is rotated between crossed nicols, indicates a radiate 

 arrangement of some birefringent mineral. In the thinnest parts of 

 the slice it can be resolved into radiating bundles of very slender 

 felspar-fibres, which seem to be impregnated and stained with 

 chloritic matter. A common radiate arrangement extends over areas 

 large enough to enclose several of the round spots mentioned, and 

 is often sufficiently complete to give a rather imperfect black cross, 

 but the areas which behave in this way interlock irregularly with 

 one another. The round spots in some places seem to have a very 

 obscure radial structure in themselves, giving sometimes a vague 

 black cross, but in genei'al they merely become darker and lighter 

 when rotated, behaving with the adjacent interstitial matter, as if 

 they shared in the larger radiate structure. In one part of the slide 

 are little prisms, mostly untwinned, of oligoclase with a fluxional 

 disposition. 



Another rock examined comes from a four-inch vein a little west 

 of the summit, and has a specific gravity of 2 806. In this [1755] 

 the little round spots are wanting, and it is seen at a glance that the 

 rock consists essentially of slender felspar-needles, about 0-03 inch 

 long, grouped in sheaf-like bundles, which interlace with one 

 another. A higher magnification shows that these little needles 

 are themselves built up of very fine parallel fibres. As before, there 

 are a few scattered felspars of larger size. The greenish material 

 is here collected into definite patches, and may probably be taken 

 to represent a destroyed pyroxenic mineral. 



Specimens showing similar features come from the face of the 

 cliff called the Scurth, at a spot about 450 yards W.S.W. of Stone 

 Ends Farm. A slice from one of these [1552] shows very beautifully 

 the sheaf-like grouping of the felspar-fibres which make up the 

 great bulk of the rock. The central part of each sheaf is composed 

 of parallel fibres, or may be compact enough to be regarded as a 

 little felspar-crystal, but spreads out at its extremities into a fan- 

 like bundle of fibres. Individual fibres give sensibly straight 

 extinction, and in one or two little prisms sufficiently developed to 

 show albite-lamellation, the largest extinction-angle measured from 



