Page:Transactions of the Geological Society, 1st series, vol. 4.djvu/137

 of which this mineral forms an ingredient. More often however their shape is perfectly defined, and they appear to be laminæ of which the edges are truncated or broken at angles with the plane. In some places this appearance of fracture is so precise, that when two fragments occur together in the granite the imagination as easily replaces the separated parts as it does in the brecciated marbles or agates: nay, further, the fragment will sometimes be found to consist of an argillaceous or slightly micaceous schistus, maintaining this character with scarcely a perceptible alteration, and sometimes only approaching to hornblende schist at its exterior parts. It is also worthy of remark that these fragments sometimes exhibit at their edges stripes of different colours and degrees of hardness, arising from the varying texture of the laminæ which compose them. The masses vary in size from an inch to a foot and upwards, but whatever their size may be they have almost invariably parallel sides. The examples of this appearance are very numerous both at Balahulish and in the rolled fragments of granite which are spread over the Black mount to the eastward of Glenco, and we shall presently see that the same granite with similar connections occupies a very large tract of country. The frequency of the occurrence also enables an observer to examine the specimens without difficulty, and to compare their various aspects and circumstances. From these I have no scruple in saying, that the granite now described contains fragments of schist imbedded in its mass, generally so altered in their original appearance by their connection with the granite, as to approach to, or partially to assume the character of hornblende slate, but often also possessing the characters of micaceous schist unchanged, and under all the varieties of aspect by which it is characterized in the surrounding country.