of St. Michael’s Mount in Cornwall. 431 
The account of these obseryations begins at p. 265 of 
the 3d volume of this work, and I shall copy such parts of 
it as will prove to Mr. Allan, that the source of his infor- 
mations was spurious. ‘ Our first remark was, the im- 
possibility that Mr. Playfair could have seen what he says, 
theveins running off from the granite of the mount, and 
spreading themselves like so many roots fixed in the schisius. 
For, along this side of the island, where the schistus or 
kellas appears, its junction with the granite rock which 
rises above it, is absolutely concealed by a heap of blocks of 
granite of such size, that it was not possible for us to pass 
over them in any part, or even to advance among them suf- 
ficiently to discover on what Lase they Sie.” 
Continuing the account of our observations, compared 
with what Mr. Playfair says of these veins: that im the 
smallest the granite is of very minute, though distinct parts, 
and that in the largest, it is more highly crystallized, and 
is undistinguishalle from the mass of the hill, ‘*This 
(I say) is by no means what we observed; for we saw two 
kinds of veins, of a nature perfectly distinct from each 
other, though intermixed: most of these veins are of white 
plots entirely pure, whatever be their breadth, some no 
ess than four or five inches; while the few others, not 
larger than the former which are among them, and which 
Mr. Playfair has taken for granite, have but a very imper- 
fect resemblance to that substance; and the following is a 
direct proof that they have not been formed by an expan- 
sion of the granite of the mount......(p. 266). In consi- 
dering the granite rocks which arose above us, we saw in 
them the most complete proof that what has the appearance 
of granite in the veins iv schistus, is not the same substance 
which composes the rocks; for these are themselves in- 
tersected by the veins of both the above described kinds; 
namely, of pure quartz, and of what I shall call pseudo- 
granite; the latter being no less distinguishable from the 
granite through which they pass than from schistus. Whence 
it is evident, that the fissures in the granite must have been 
contemporary with these in the schistus below.” This cir- 
cumstance, had Mr. Allan known it, by reading my own 
work, would have shown him, that the specimen from the 
veins of St. Michael’s Mount which he exhibited to the 
Edinburgh Society, instead of proving that I was deceived 
in that place, confirmed my observations,—with this dif- 
ference, that in so small a specimen he could not distin- 
guish so evidently the difference between the substance of 
the 
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