10 y. A. PHILLIPS OIT CONCEETIONAKY PATCHES AND 



rous small patches of red ortlioclase, contains a large crystal of 

 that mineral, the angles of which are rounded. 



A large dark-coloured fine-grained patch observed in this rock 

 contains a smaller one considerably lighter in colour and presenting 

 very distinct outlines. Besides imperfect and much-rounded crystals 

 of red and white felspar, this specimen encloses a large milky felspar 

 crystal of which the angles are perfectly sharp. 



Six sections were examined, from as many rounded enclosures, 

 from the Shap quarries, and, without exception, the ground-mass of 

 the whole of them was found to contain all the various minerals 

 constituting the normal granite of the district, although the pro- 

 portion of dark mica present was in considerable excess. Triclinic 

 felspar appears to be more abundant in the inclusions than in the 

 surrounding granite, and a portion of this mineral shows cross 

 striation in polarized light ; a few of the crystals exhibit concentric 

 lines of growth. 



In exceptional cases the patches in Shap granite, from the almost 

 total absence of black mica, are lighter in colour than the surround- 

 ing rock ; and occasionally two distinct inclusions, differing both in 

 texture and colour, are found one within the other. 



In addition to the rounded masses already described, this granite 

 encloses others of a more schistose character, which are often softer 

 than the rock in which they are contained. Sections of inclusions of 

 this kind are seen under the microscope to consist either entirely of 

 mica, or of mica associated with quartz and occasional crystals of 

 felspar. "When composed of mica alone, these inclusions can scarcely 

 be regarded otherwise than as being of segregationary origin ; but 

 where quartz in considerable quantity is also present a fragment of 

 mica-schist may sometimes have become enclosed in the granite. 



The method of occurrence of such bodies in Shap granite will be 

 understood by reference to PL I. figs. 4, 5, natural size, care- 

 fully drawn by 'Mr. Prank Eutley. Whether these be the result 

 of included flakes of a stratified rock, or of the segregation of mica 

 only, it is evident that they must have been at least partially con- 

 solidated previous to the crystallization of the felspar. It will 

 be observed that in fig. 4 the inclusion is completely divided by 

 a large crystal of orthoclase, while in fig. 5 a crystal of that 

 mineral is traversed by fragmentary portions of a similar body. It 

 is somewhat unfortunate that, as the drawings were made from a 

 polished pillar, it was impossible to obtain thin sections of these 

 particular inclusions. 



Scotch Granites. — The Scotch granites of which I have examined 

 the inclusions are those in the neighbourhood of Aberdeen, Peter- 

 head, and Port William. 



The Aberdeen granites are grey in colour and fine in grain, and 

 are mainly composed of quartz and felspar, with colourless and dark 

 or nearly black micas. The granite of this district is regarded by 

 Prof. Haughton as being of metamorphic origin*, and is apparently 

 almost free from rounded or pebble-like inclusions. 

 * Proc. Eoy.Soc. vol. xviii. p. 313. 



