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The torrent-beds are of the clearest and finest white sand, glittering with gold-coloured mica, and varied with nodules of clear and milky quartz, red porphyry, and granites of many hues.
Kevern's paten and chalice, arose in the night and fled away with the holy vessels, wading first the Looe Pool, and then Mount's Bay itself; and how St. Kevern pursued him, and hurled after him three great boulders of porphyry, two of which lie on the slates and granites to this day; till St. Just, terrified at the might of his saintly brother, tossed the stolen vessels ashore opposite St.
Hence, we must not expect to find the Recent or even the Pliocene granites laid open to view, unless we are prepared to assume that sufficient time has elapsed since the commencement of the Pliocene period for great upheaval and denudation.
In this comprehensive glance we may also notice the shallow wind-worn caves in stratified sandstones along the margins of the plains; and the cave-like recesses in the Sierra slates and granites, where bears and other mountaineers find shelter during the fall of sudden storms.
No one can travel there without becoming tiresomely familiar with fine-grained, shattered schists, coarse granites, and their curiously banded relatives, the gneisses. This rocky highland stretches from a little north of the St. Lawrence River to Hudson Bay, around which it laps in the form of a V, and so is known as the Archaean V or shield.
Some have imagined that the age of different granites might, to a great extent, be determined by their mineral characters alone; syenite, for instance, or granite with hornblende, being more modern than common or micaceous granite. But modern investigations have proved these generalisations to have been premature.
Some are of the normal basalt, which may also have served for crushing grain; others are cut out of grey and ruddy granites: a few are the common Mahrakah or "rub-stones," and the many are handmills, of which we shall see admirable specimens further on. One was an upper stone, with holes for the handle and for feeding the mill: these articles are rare.
The red granite, black sienite, and red porphyry of Egypt, which are seen at Rome in obelisks, columns, and sarcophagi, are amongst the most durable compound stones; but the grey granites of Corsica and Elba are extremely liable to undergo alteration: the feldspar contains much alkaline matter; and the mica and schorl, much protoxide of iron.
These mighty agents of erosion, halting never through unnumbered centuries, crushed and ground the flinty lavas and granites beneath their crystal folds, wasting and building until in the fullness of time the Sierra was born again, brought to light nearly as we behold it today, with glaciers and snow-crushed pines at the top of the range, wheat-fields and orange-groves at the foot of it.
The quadruple compound of quartz, feldspar, mica, and hornblende, may be termed Syenitic Granite, and forms a passage between the granites and the syenites. This rock occurs in Scotland and in Guernsey. We now come to the second division of the Plutonic rocks, or those having less than 60 per cent of silica, and which, as before stated, are usually called syenitic.
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