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 120 granite. An interrupted line of quartz rocks borders the western side of the gneiss tract from Loch Eribol to the southern parts of Skye. The primary limestones occupy but little surface.

From the Argyleshire highlands the mica schist may be considered as crossing the Channel, south-westward, to Derry and Donegal, where it expands into the large area adjoining the sea, from Lough Foyle to Ballyshannon, and stretches inland nearly to border the basaltic platform of Antrim, being associated with granite, quartz rock, limestone, and old red sandstone. From Donegal Bay to the Bay of Sligo, and from this nearly to the Bay of Galway, mica schist with quartz rocks occupies a great part of the mountainous borders of the Atlantic. The Wicklow granites are bordered by narrow belts of gneiss. Excepting very insignificant traces in Skiddaw, there is hardly any real gneiss or mica schist in England or Wales.

To describe the extent of country occupied by gneiss and mica schist on the continent of Europe, would, perhaps, be impracticable, and certainly, in an English treatise, of little use; the Pyrenees, the Alps, and the great chains of Bohemia and Scandinavia, are full of these rocks, which have much the same characters as in the Grampians and Connemara; rest in the same way on granite (which enters them in veins); are similarly associated with limestone, quartz rocks, and serpentine; and are equally deficient of organic remains. Most of the great mountain chains of the world contain these rocks, and they may be considered as the most nearly universal strata that we are acquainted with.

Physical Geography.—Usually exhibited at high angles of inclination along the axes or flanks of great mountain elevations, gneiss and mica schist, with their associated rocks, derive from this circumstance a grandeur of position which gives full effect to the bold summits, abrupt precipices, deep glens and lakes, which abound in these tracts. The pointed gneiss rocks near Mont Blanc (Aiguilles),—the conical tops of the quartz mountains of Schihallion,—the Paps of Jura,