Page:Transactions of the Geological Society, 1st series, vol. 2.djvu/125

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115
Mr. William Phillips on the Veins of Cornwall.

in Cornwall in layers or beds. The veins, in which only they are found, have a downward direction, not perfectly perpendicular to the horizon, but inclining more or less to the North or South; this inclination is called the underlie of the load, which in some veins does not exceed a few inches in a fathom from the perpendicular, but in others is a fathom in a fathom, or even more.

When two metalliferous veins underlie in opposite directions, that is, one North and the other South, and meet underground, the result is not always favourable to the miner; for even though they might have been rich when separate, they generally are found to be poor at and after their junction. But when two lodes underlie in the same direction, and one of them quicker than the other, it is generally found that when the latter overtakes the former, they seem mutually to enrich each other.

Veins are not very frequently found to separate in the downward direction, so as to make branches forming distinct veins, having an opposite underlie. Instances of this however occurred in Tin Croft Mine, of which a Section is given.

Depth of Veins.

Not an instance, I believe, has occurred of a vein having been cut out in depth. When the working of a mine is relinquished, it is mostly either on account of its poverty, or the expense of sinking to a greater depth, being to a larger amount than the product. The mine called Crenver and Oatfield is 200 fathoms deep; Cook's Kitchen is 210; and Dolcoath 228 fathoms; these are the deepest mines in the county now at work.


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