204 E. HILL AND T. G. BONNEY ON THE 



composed ; several grains of quartz ; presence of lapilli uncertain ; 

 rest much as usual. 



Bensdiff Agglomerate (p. 765). — Here also the lapilli are less 

 distinct than usual, and there is rather less epidote ; quartz grains 

 &c. as usual. 



Matrix of Whitwick Breccia (p. 779). — A finely comminuted fel- 

 spathic ground-mass, rather similar to, but more uniform than, 

 those above described, speckled with minute ferruginous granules ; 

 viridite and epidote rather abundant, the latter often aggregated. 



Of the last seven rocks there is reason to think, as already stated, 

 that the first six belong to the same group, though not necessarily 

 to exactly the same horizons in it. Microscopic examination reveals 

 nothing opposed to this, and shows that the Kite-Hill, BensclifT, and 

 Timberwood-Hill rocks have a close resemblance. The Green-Hill 

 and Barnby-Wood rocks differ somewhat, and the Monastery rock 

 is distinguished by distinctly andesitic fragments. The Whitwick 

 rock may be allied to the first three, but there is little positive 

 evidence. 



From these numerous instances we seem to be justified in drawing 

 the following conclusions : — 



(a) That these coarser Charnwood rocks are generally pyroclastic. 



(6) That they contain numerous lapilli still easily recognizable. 



(c) That the majority of these belong to one of the more acid 

 plagioclase lavas, probably andesite. 



(d) That the larger felspar crystals are of clastic origin, and not 

 subsequently formed by metamorphism of the ground-mass. 



(<?) That the quartz also is of clastic origin. 



(4) Highly altered Rock, Ratchet Hill (p. 777). — We may take 

 this as typical of the highly altered felspathic rocks common in the 

 N.W. district of Charnwood Forest. They have a compact, slightly 

 porphyritic ground-mass of a purplish-grey colour, and a rather 

 flaky aspect, due to imperfect cleavage. The ground-mass of the 

 slide is partially translucent, but thickly crowded with minute 

 brownish granules irregularly aggregated. With crossed Mcols it 

 shows a dark base crowded with very minute transparent belonites 

 not clearly defined ; grains of magnetite or ilmenite are present, more 

 or less decomposed ; patches of viridite often studded with aggregated 

 crystals of yellow epidote, which mineral is also found minutely dis- 

 seminated ; a chloritoid mineral is also present ; the outline of these 

 patches of viridite and epidote suggests that they are secondary pro- 

 ducts after some such mineral as augite or hornblende. It would 

 not be safe to say more than that this rock is of clastic origin. 



Peldar-Tor Rock (p. 776). — This remarkable rock has a compact 

 felstone-like greenish- to purplish-grey ground-mass, crowded with 

 ill-defined, rather pale red, lustreless felspar crystals, and numerous 

 grains of quartz, often showing imperfect crystal faces. The felspar 

 crystals are generally squarish in form, attaining full 0*3 inch in 

 diameter, about the same as the quartz grains. Under the micro- 

 scope the ground-mass is rather variable. It resembles a transparent 

 glass more or less crowded with exceedingly minute dusty brown 



