24* GRANITIC ROCKS OF OTHER COUNTK1ES [Ch. III. CHAPTER III. THE GRANITIC ROCKS OF OTHER COUNTRIES COMPARED WITH THOSE OF CORNWALL. Descriptions of these rocks neither numerous nor circumstantial. — The granite of Aberdeenshire characterised by its hornblende — its varieties.—The association of granite and porphyry in the mountain Cruachan,— and of granite and quartz-rock near Glen Tilt. — The granitic district of the eastern part of Ireland, — it abounds in quartz, — and is characterised by mica. — Granitic rocks of the Erzgebirge, at Freyberg, Altenberg, and Zinn- wald. — Granite of the Hartz mountains also micaceous, — its nature doubt ful,— interstratified with schistose rocks. — Remarks on the binary compounds of quartz with shorl, mica, or talc. Having examined the granitic rocks of Cornwall, it is now proposed to turn our attention to those of other countries, in order to ascertain whether their constituent minerals are similarly aggregated together; and whether the masses re sulting therefrom are subject to the same arrangements. The details, however, on this head are not so circumstantial as might be desired: this deficiency is attributable to two causes; first, to the indisposition of geologists to enter into mineralogical minutiae, which they have hitherto con sidered in this country to be comparatively unimportant > and, secondly, to the want of such favourable opportunities for investigation as occur in the cliffs of Cornwall. Notwithstanding the paucity of such descriptions, yet suffi cient data may be gleaned for our purpose, which is to show, that the granitic rocks of other countries exhibit similar variations in their mineral composition, and similar associations as those of Cornwall. We learn, from the excellent descriptions of the primary rocks of Scotland by Dr. Macculloch, that the granitic masses are analogous to those of Cornwall: they have not, indeed, the same composition, for hornblende, not shorl, is their