NORTH-WEST REGION OF CHARNWOOD FOREST. 93 



however, plead in excuse that some of the most important evidence 

 was disclosed by quarrying subsequent to our visits, and that it is 

 only during the winter and early spring that the hill itself can be 

 readily examined, as it is so much overgrown during the rest of 

 the year by brushwood and coarse herbage. 



On the last occasion a dyke of granite, some 4 feet wide, was ex- 

 posed, running from the top almost to the bottom of the north- 

 western wall of the pit, where it was still concealed by the micaceous 

 rock. There was also another mass, not so well exposed, in the 

 S.W. wall, and the end of a vein just showed itself in the wall 

 between these. We are certain that these junctions were concealed 

 at our visits prior to 1877, and the great dyke was not visible even 

 a year or two later than that date. We were able to examine 

 carefully the knoll at the back of the pit, and found several small 

 low^ outcrops of the " micaceous rock." For a few yards this does 

 not seem to differ from the rock in the pit ; then it becomes less 

 coarsely crystalline, after w^hich a fissile zone occurs *, and about 4 

 yards farther, at the base of the knoll (which runs roughly N.IN'.W.- 

 S.S.E.) some thirty yards in a straight line from the edge of the pit, 

 is a purplish slaty rock, which macroscopically does not seem much 

 altered. We have examined, microscopically, specimens of these rocks 

 in order to study the effect of the contact-metamorphism. Com- 

 mencing with the last-named ; — it exhibits a minutely speckled 

 groundmass, consisting of tiny plates of brown mica, of white mica (?) 

 (this is the more abundant mineral, and sometimes is aggregated in 

 small patches with uniform extinction), and of a colourless mineral, 

 probably in part at least quartz ; here and there is a larger grain 

 of a colourless mineral, quartz or some silicate. Through the 

 groundmass run trailing aggregates of irregular form, which some- 

 times enclose small, rather oval, patches of it, and consist of brown 

 mica-flakes from about -001 inch long, at a maximum, downwards. 

 In one part of the slide flakes are grouped in tiny clusters, more or 

 less circular in outline, round which is a clear narrow ring of the 

 colourless mineral (chalcedonic quartz ?) ; granules of brown iron 

 oxide also occur. The streaky aggregates exhibit a slight tendency 

 to parallelism, but there is no true foliation ; the slide, however, 

 exhibits some iron-stained cracks, indicative of a rude cleavage. 

 The specimen on the whole presents a general resemblance to that 

 described from near the contact at Enderby f. 



A slice cut from a specimen about ten yards nearer the edge of the 

 pit is more coarsely crystalline, the mica flakes being generally twice 

 or thrice the former size, especially in the case of the white mica, 

 which is now a much more conspicuous object ; the peculiar clotted 

 and spotted aspect of the rock is almost lost, and several garnets 

 occur, approximately from *02 to -03 inch in diameter. Near the 

 junction the rock becomes yet coarser in texture, the garnets measuring 



* The sti'ike of the cleavage is given in Messrs. Allport and Harrison's 

 paper, Mid. Nat. vol. ii. (1879) p. 243, as N.W.-S.E. 



t Quart. Journ. Geol. See. vol. xxxiv. (1878) p. 227. 

 a.J.G. S. Xo. 186. H 



