260 MR. E. H. RASTALL OK THE [May I906,. 



showing rather stronger double refraction may be referred to 

 clinochlore. However, for all practical purposes it is sufficient 

 to regard it as chlorite derived from original biotite. Description 

 of the chlorite derived from augite may be deferred, until the local 

 modifications in which it occurs are dealt with in detail. 



Some common accessories are magnetite, apatite, sphene, zircon r 

 epidote, and calcite : they do not call for any special remark. The 

 calcite is always secondary, and so is probably some of the epidote ; 

 however, the inclusions of epidote in the chlorite may be original. 



A slice [4762], taken from near the margin of the small mass 

 which lies on the hillside west of Buckbarrow, shows a remark- 

 able facies. Instead of being, as we might expect, of very fine 

 texture, it is the coarsest and most granitic type yet obtained. 

 The rock is almost free from coloured minerals, only a very little of 

 the ordinary chlorite being present. It consists of a coarse-grained 

 aggregate of various felspars and quartz, with typical hypidio- 

 morphic granular structure ; in places only is there a very slight 

 tendency to graphic intergrowth of the quartz and felspar. There 

 is a large amount of felspar showing albite- twinning, and belong- 

 ing to oligoclase-albite and albite. The remainder is perthite, in 

 less perfectly-formed crystals, which very frequently have a cross- 

 hatched character, resembling that of microcline in certain sections, 



Specimens taken from the southernmost or highest laccolite show 

 the same type of structure as that which is seen in the marginal 

 parts of the larger masses on the north ; and they may be described 

 briefly as belonging to the granitic type, with only very slight 

 indications of micrographic intergrowth. Their texture is not 

 conspicuously finer, and felsitic modifications are not found to any 

 extent. The small hill known as Berry How, about half a mile 

 north of Strands, consists of a reddish rock, which in the field 

 appears to resemble strongly the felsitic rock of Hevlin Crag and 

 Silver Cove ; but, under the microscope, it is seen to be identical 

 with the metamorphosed Borrowdale volcanic rocks of other parts 



the district. 



(b) Felsitic Modifications. 



In some localities, as at the head of Silver Cove [4754] and on 

 Revlin Crag, the rock becomes very fine in texture, and in hand- 

 specimens presents a felsitic appearance. In slices it sometimes 

 shows a slight tendency to porphyritic structure. These fine-grained 

 varieties vary considerably in composition. In the specimen from 

 Eevlin Crag quartz is practically absent ; whereas at Silver Cove it 

 is abundant. The felspar is generally much decomposed, and coloured 

 minerals are practically absent. These felsitic modifications are 

 all marginal, and may be regarded as chilled edges. 



