Vol. 65.] IN THE NEIGHBOURHOOD OF ESKDALE. 63 



structure. In other eases the micropegmatite is very coarse-grained, 

 and not definitely connected with any phenocryst of felspar. 



In several instances, as noted by Dr. Teall, 1 quartz is included 

 in felspar, and this applies equally to orthoclase, perthite, and 

 oligoclase. 



An instance of quartz embedded in oligoclase is illustrated by a 

 specimen from Mitredale Head (66). (See PI. Ill, fig. 2.) 



Further evidence of this abnormal order of separation is to be 

 found in some of the fine-grained varieties near the margins of the 

 intrusion, where phenocrysts of quartz, in one instance corroded as 

 in the quartz-porphyries, occur in a quartz-felspar matrix (PL III, 

 fig. 3), and in the fact that the extreme margins of the laccolite, 

 the first portions to solidify, consist of almost pure quartz. (See 

 chemical analysis, p. 64.) 



Secondary Minerals. 



Haematite is present as a secondary mineral, and occurs in veins 

 and patches ; while in some instances it forms a fringe round the 

 crystals of quartz and felspar, and in others impregnates crystals 

 of muscovite where they are crossed by cracks (3). 



Cracks filled with secondary quartz, in a fine mosaic, are occa- 

 sionally seen to cross crystals of felspar. Chlorite is a common 

 decomposition-product of biotite in the more weathered specimens. 



Petrology of some Varieties of the Granite. 



The Wabberthwaite variety (182). — This is a medium- 

 grained dark-grey granite, in which biotite is much more plentiful 

 than in other localities. 



It consists of quartz, orthoclase (kaolinized), and a smaller 

 quantity of perthite, with considerable quantities of biotite in a 

 fairly fresh condition, and subordinate muscovite. The order of 

 separation of the minerals seems to be normal. 



There are also numerous veins of aplite in the Wabberthwaite 

 Quarries. 



At Stainton-Mill Dam (183) is a small exposure of a pink 

 granitoid rock, which is unlike anything met with in other parts of 

 the area. Under the microscope it is similar to the Wabberthwaite 

 variety of the granite, except that it contains considerable quantities 

 of a pale-green pleochroic amphibole. 



The exposure is small and its boundaries are not seen, hence it 

 is impossible to determine its relation to the normal variety; but, as 

 it occurs in the midst of the granite-mass and possesses many 

 characters in common with it, it does not seem probable that it is a 

 separate intrusion. It may possibly be due to the inclusion and 

 absorption of a mass of the country-rock (Borrowdale andesite) as 

 described by Dr. K,. A. Daly (Am. Journ. Sci. ser. 4, vol. xxvi, 1908, 

 p. 19) ; but, if so, it is the only evidence of this action that I have 

 seen in the district. 



1 ' British Petrography ' 1888, p. 323. 



