CRYSTALLINE SCHISTS OP THE MALVERN HILLS. 531 



3. About 15 feet of schistose rock, forming a band below No. 2, 

 but continuous with it. Some of it is hardly distinguishable from 

 the rock above, but the laminated structure is more evident. In 

 other seams the foliated appearance is more marked, and a complete 

 gradation can be traced between the modified felsite and a true 

 schist. The change is seen even on the ground in the increasing 

 distinctness of the lamination proceeding pari passu with the 

 growing thickness of the films of mica on the planes of fissility. 

 These indications are entirely confirmed by the microscope. The 

 following gradation is seen in three specimens taken from the same 

 band, within a yard or so from each other. 



No. 294. Felsitic appearance in hand specimens, but slightly 

 laminated. Under the microscope the parallel structure is seen to be 

 due to intermittent folia of a green mica, in irregular bundles of 

 fibres and sometimes dirty. This part of the rock also must have 

 been a porphyry, for the slide shows several eye-shaped masses of 

 crushed quartz which have caused the folia of mica to curve out of 

 their course, forming, as it were, eyebrows to the quartz, both above 

 and below, just as in the crushed granite described above (p. 529). 

 Some parts of the slide display the felsitic structure, as above ; but 

 where the mica is most abundant the granules of the ground-mass 

 are often of larger size and polarize in bright colours. Mineral 

 differentiation would thus appear to have proceeded a stage further. 



No. 295. The change in the felsite is more advanced. The rock 

 chiefly consists of elongated granules of quartz arranged in a linear 

 manner, with mica lying between them in microliths, so as some- 

 times to form a partial sheath. Some of this mica is transparent, 

 polarizing in bright colours. Patches of the same mica and some 

 felspar are also present. Distinct seams of mica and felspar, parallel 

 to the longer axes of the quartz-grains, accentuate the foliation. 



No. 296 is generally similar to the last. In about the middle of 

 the slide is a very quartzose seam, in which the grains are much 

 larger than in the previous specimens. It is not a vein, but a true 

 folium, parallel to the rest. It passes by the gradual introduction 

 of mica into a broad, very micaceous band, which graduates in- 

 sensibly into a zone displaying a structure strongly suggestive of the 

 micro-felsite, but a few microliths of clear mica are present. Some 

 parts of the hand-specimen also have a very felsitic look under the 

 lens. 



No. 299 is from one of the several narrow micaceous bands inter- 

 laminated with the more quartzose schist. It is an indubitable 

 mica-schist. The mica is the white variety. It forms about half 

 the mass, a great part of it being in distinct folia, which sometimes 

 undulate. Some of the quartz has the same appearance as in Nos. 

 295, 296,- the granules being more or less sheathed with mica. A 

 few lenticular " eyes " of quartz are rather suggestive of the crushing 

 -of a porphyry ; but on this I do not speak decisively. I am quite 

 satisfied, from a very careful study on the ground, that these 

 micaceous seams cannot be regarded as foreign fragments of schist 

 entangled in the crushed felsite. 



