Page:Transactions of the Geological Society, 1st series, vol. 2.djvu/147

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137
Mr. William Phillips on the Veins of Cornwall.

Heave.

Transactions of the Geological Society, 1st series, vol. 2 figure page 0589 fig. 7.png

But when the underlie of this species of vein is in opposition to that of the metalliferous vein, the effect of it is immediately the reverse of that of the Slide, and is called the Heave. Pryce has noticed a remarkable instance of this which occurred in the Goon Laz and Pink tin mines, in the parish of St. Agness. The tin load underlaid north, the gossan vein south. (Pl. 7. fig. 7.) At 62 fathoms in depth, it separated the tin load at a, heaving the other part of it up to b, 22 fathoms in perpendicular height, and 19 fathoms horizontally north. Another gossan vein afterwards cut the tin load at c, heaving it up to d. The tin load then resumed its course, until another gossan vein separated it at e, heaving it up to f.

It will be observed that the effect of the heave is than of affording a greater portion of the tin load at a given depth from the surface, than would have been the case had the vein pursued its regular downward direction. But this is not always a compensation to the miner; for the vexation and expense accruing to him in searching for the tin vein generally exceed any advantage to be gained by the heave. It was, I believe, principally the effect of a heave that baffled the skill and experience of the most eminent practical miners in Huel Peever; in which mine they were, during about 40 years, in search of the load, and which was at length discovered. Perhaps the history of that mine, and of the long and vexatious search, occasioned by the loss of the vein, would prove the most satisfactory evidence that can be obtained of the strange phenomena occasioned by the heave; and I have the satisfaction of knowing that it is the intention of a gentleman, who has nearly

Vol. II.S