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with extensive strata of clay-slate, quartz rock, or mi caceous schist; and this leads me to enquire into the philosophy of the appearances in question. They who have called these veins contemporaneous, are of those who write phrases without ideas ; and they who have supposed them independent of granitic con nected masses, have wanted industry or capacity to examine them. I have traced these veins to their parent masses wherever a mass existed; and where they cannot thus be followed, it is because the funda mental granite is out of sight and reach. If the uni versal inference is not safe, it may be asked what and whence is a granite vein. Let me also remark, that in numerous parts of Scotland, where the leading masses of gneiss are schistose, evenly stratified, and scarcely ever traversed by granite veins, they become contorted and irregular as they approach the granite; assuming also the granitic character, and becoming intersected by veins, numerous in proportion to the vicinity of the mass. The conclusion is almost too obvious to require being stated; and it implies the most essential part of the theory of gneiss. The fluid granite has invaded the aqueous stratum as far as its influence could reach, and, thus far, has filled it with veins, disturbed its regularity, and generated in it a new mineral character, often absolutely confounded with its own. And if the more remote beds, and those alternating with other rocks, are not thus affect ed, it is not only that it has acted less on those, but that if it had equally affected them, they never could have existed, or would have been all granitic and venous gneiss. Thus are its varieties of character, even to its absolute transition into granite, explained. Though the general facts have formerly been stated, it is necessary to mention, as part of the history of VOL. II, h