THK SHAP GIUNITK AND ASSOCIATED KOCKS. 323 



enclosed by them, are patches of rounded p:ranules, highly refringent 

 and birefringent, which must be referred to a pyroxene, probably 

 the lime-augito already frequently alluded to. These granules are 

 mainly collected at the margin of the fragments or in the neigh- 

 bourhood of little vein-like cracks. 



The angular pieces of flag show a marked lamination defined by 

 streaks of opaque dust. Their metamorphism is similar to that 

 of the corresponding rocks in situ, except where the fragments are 

 traversed by cracks and veinlets, which evidently represent a per- 

 meation by carbonate of lime and other substances. In these places 

 a number of special minerals may be detected, lime-silicates pre- 

 dominating. The usual colourless augite is abundant in irregular 

 crystalline patches, often accompanied by clear felspar and probably 

 quartz. There are also streaks composed entirely of a minutely 

 matted aggregate of rather fibrous tremolite [1285]. Near these 

 there is frequently a pale yellow-brown pleochroic mica, in clusters 

 of small flakes. A pyrites mineral occurs among the tremolite and 

 felspar, and by its colour would be assigned to pyrrhotite. 



The metamorphosed fragments of the more calcareous flags in the 

 breccia generally show a finely granular mass, mostly polarizing in 

 bright tints, but too minute to be precisely determined. The 

 general character of the mass may, however, be inferred from those 

 constituents which are here and there developed in larger crystalline 

 patches. Of these the most usual is colourless augite, readily 

 identified by its cleavage, extinction-angles, and interference-colours. 

 Another conspicuous mineral is light brown, pleochroic sphene, 

 which occurs plentifully in grains and good crystals (habit, n, c, y) 

 scattered through the fragments. 



The cementing material of the breccia is almost exclusively 

 colourless augite, building a relatively coarse-grained crystalline 

 aggregate, and enclosing plenty of little sphene crystals [1286]. 

 This cement makes up on the whole a small part of the mass, and it, 

 with the smaller veins traversing the fragments, clearly represents a 

 calcareous infiltration filling the interstices of the original fault- 

 breccia. 1^0 calcite now remains. 



In conclusion we may note one or two points with reference to 

 the metamorphism of the Shap Pell rocks as a whole. The pro- 

 duction of new minerals is confined to distances of not much more 

 than 1200 or 1300 yards from the granite-contact, or about equal 

 to the mean semidiameter of the intrusive mass itself as exposed at 

 the surface. The width of the metamorphic aureole, as thus defined, 

 seems to be tolerably uniform in different directions from the 

 granite. Moreover, this extreme limit of metamorphic action is 

 very nearly the same, whether we consider the andesitic rocks, the 

 rhyolitic ashes, the various calcareous strata, or the Brathay Flags. 



Within the metamorphic aureole the changes increase in degree 



