ASSOCIATED METAMOEPHIC EOCKS OP THE LAEE-DISTEICT. 21 



regard the rock as part of an original lava-flow, with the minutely 

 crystalline structure so common in that class of rock in this country. 

 Whether the spherulitic felsite may be a further step in the altera- 

 tion of somewhat similar beds, shall be considered when the other 

 two divisions of the Carrock rocks have been described. 



4 b. Diorite (?), altered dolerite (Round Knott and Miton Hill). — 

 This generally fine-grained, dark, crystalline rock, presents a beau- 

 tiful appearance under the microscope. Even specimens taken from 

 that part of the rock at Eound Knott which shows traces of bedding, 

 have a fine crystalline microscopic structure, consisting of felspar, 

 mostly plagioclase, a hornblendic mineral, and some nearly unaltered 

 augite, and more or less quartz, probably of secondary formation. 

 But, from the manner of occurrence of the green hornblendic 

 mineral, and the indications of partially altered augite, one would 

 be inclined to suspect that the rock may be an extremely altered 

 one, belonging, in parts at any rate, to the doleritic class * 



Looking at its microscopic structure alone, one would but little 

 expect to find such a rock having well-marked lines of bedding. 



4 c. Hyperstlienite (altered dolerite ?), south of Carrock-Fell 

 summit, crags above and north of Mosedale Village, Lang Dale, and 

 Balliway Rigg. — This rock presents the following general micro- 

 scopic characters. A coarsely crystalline compound of plagioclase 

 felspar and hypersthene, with scattered grains of titaniferous iron 

 oxide, and more or less quartz. The dark-green, coarsely crystal- 

 line varieties of the rock show little or no quartz ; but the white or 

 grey varieties (lighter-coloured felspar) contain a good deal, occu- 

 pying spaces between the other minerals. The hypersthene may be 

 replaced by a hornblendic mineral or may occur in conjunction with 

 it. Fig. 7 (PI. II.) represents the microscopic structure of the white 

 variety from White Crags (an analysis of which is given in this paper) 

 as viewed by polarized light. The quartz is seen in triangular and 

 other spaces between the banded plagioclase crystals ; and part of 

 an altered crystal of hypersthene is shown with patches of the 

 black iron oxide. 



Mention has been made of the apparent stratification in this rock, 

 immediately south of Carrock Fell and Eound Knott. The coarse 

 bands are, microscopically, a crystalline mixture of plagioclase and 

 hypersthene ; but the fine-grained bands, which alternate with the 

 former, show a very different microscopic structure. This I have 

 endeavoured to reproduce in fig. 8, as seen in polarized light, 

 between crossed Mcols. In ordinary light a great number of w T ell- 

 defined grains, clear and transparent, are seen to be closely touching 

 one another or parted by a green dichroic mineral, and minute 

 particles of magnetite to be scattered plentifully throughout. Be- 

 tween crossed Nicols, the clear grains are seen to consist of partly 

 crystallized felspar and quartz, besides which there occur some 

 crystals of plagioclase of a larger size ; and the green mineral seems 

 to be in part hypersthene, and in part, probably, hornblende and 



* This was Mr. Allport's opinion when he kindly glanced through these 

 slides. 



