OP THE MALVERN HILLS. 



503 



-or less at right angles to the foliation. There is something more 

 than accident in this circumstance. By reflected light, a rusty 

 brown colour is seen to pervade the darker bands of the rock, and 

 the darkness of these bands appears to be due partly to the presence 

 of biotite, and partly to that of limonite. The rock is essentially a 

 biotite-gneiss. 



No. 27. Sivinyard's Hill, largest Quarry, South end. — Dark grey, 

 finely foliated micaceous rock. On a cut surface, blotches and 

 streaks of a flesh-red felspar are visible. The rock has an imper- 

 fectly fissile structure, and on the schistose planes the micaceous 

 character is, of course, most perceptible. 



The description of the microscopic characters of the preceding 

 specimen applies equally well to this, except that there is more 

 muscovite present, and it is still noteworthy that the streams of fluid- 

 enclosures in the quartz again rim in a direction roughly normal to 

 that of the foliation. 



The rock is a biotite-muscovite-gneiss. The foliated structure of 

 this rock is shown in PI. XX. fig. 11. 



No. 28. Raggedstone Hill, Eastern Spur at top of hill near the 

 middle, and at the northern end. — A fine-grained, greenish-grey, 

 micaceous, schistose rock. 



Under the microscope, quartz, a little felspar, muscovite, and 

 kaolin appear to be the principal constituents. The quartz occurs 

 in grains and aggregates of grains, which have a lenticular form, 

 and the mica scales lie in wavy films, which separate these lenticular 

 bodies and impart a wavily streaked appearance to a section taken 

 transversely to the schistose structure of the rock. These micaceous 

 streaks are rendered more distinctly visible by an opaque yellowish- 

 white substance which accompanies them, and is probably kaolin. 

 Small scales of mica are also seen traversing individual grains of 

 quartz. The quartz contains numerous fluid-lacunas, and these, again, 

 frequently lie in streams which in most cases follow directions more 

 or less steeply inclined to the general direction of the micaceous 

 bands. 



The rock is a mica-schist. Its foliated character is shown in 

 PI. XX. fig. 12, where the darker markings represent the micaceous 

 bands. 



No. 29. SwinyaroVs Hill, large Quarry, South end, at foot of hill. — 

 An essentially micaceous rock, in colour reddish brown to grey 

 transverse to the direction of fission, but greenish grey, from the pre- 

 dominance of mica, along the planes of fission. The fissile structure 

 is very irregular. 



The microscope shows the presence of quartz, felspar, biotite, here 

 and there a grain of magnetite, natrolite, and a very little limonite. 

 Some of the felspar shows t win-lam ellation, but it is nearly all in an 

 advanced stage of alteration. It appears to be microcline, as a rule. 

 The biotite is of a greenish colour, and runs in irregular bands. 

 The quartz is in irregularly-bounded crystalline grains, through 

 which run streams of fluid-enclosures at right angles or obliquely to 



