Page:Transactions of the Geological Society, 1st series, vol. 2.djvu/124

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Mr. William Phillips on the Veins of Cornwall.

circumstances of disaster, and more particularly that of poverty, occur to prevent their extent from being known; but that there are instances of their appearing not to exceed a few fathom: in length, is evinced by the ground plans of Herland and Drannack mines, accompanying this paper. In reality however the veins of those mines did not terminate as represented on that plan, but continued both East and West, to an unknown extent, in strings so very small, as to be only just perceptible, and therefore not worth the attention of the miner, whose experience induces him to believe that when a vein diverges in metalliferous strings, however small, they would, if pursued, be found ultimately to increase in size, or to converge again, or to diverge to other veins, which are generally found to be, as it were, increased in size and value thereby. The East and West veins are sometimes found diverging from the straight line, even when apparently unaccompanied by any circumstance that might be assumed as the cause, but they generally return and resume their customary direction. In Huel Fanny, I think, the vein suddenly took a course to the South-East, in a few fathoms it was found to alter its course again, nearer East; afterwards it ran about East, and then elbowing again, it resumed its usual direction, nearly if not quite in a straight line. But circumstances of this kind are by no means common.

Underlie of Veins.

With the exception of those alluvial depositions of tin, found in vallies and low grounds in many parts of the county, and in the working of which the tin is separated from its accompanying earthy substances by means of passing a stream of water over it, whence they have been called stream works, neither copper nor tin is found