Page:Transactions of the Geological Society, 1st series, vol. 2.djvu/160

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Mr. William Phillips on the Veins of Cornwall.

the drawing of the water being performed by the engines on Herland mine, and the name Drannack was added to Herland because two of the Mines (Fanny and North Herland) united with it were situated in a tenement of that name. This section therefore is that of the workings of the veins designated on the ground plan by the names of Pleasure, Fancy, and North Herland, north, middle and south branches. It is on the course of those veins, and supposes the country on the south side of them to be taken away, and of course in looking at this section we look north.

The shafts and levels which constituted the workings of these mines are not laid down, because they were not completed on the original, and even had they been so the present object can be as well accomplished without them. This section, together with the accompanying section of Herland mine, exhibits several striking geological facts.

By this section the underlie of the several north and south veins, or cross courses and flucans, which intersected the mines, will be observed.

It will also be seen that, to use the miners language, a large channel of elvan took its course with a very quick underlie towards the west: near the surface it was about 15 fathoms thick, but diminished gradually in depth. Its precise direction or extent on the surface towards the north and south was not ascertained. From some specimens of this channel in my possession, and of that passing through Herland mine, they appear to consist of crystals of quartz and felspar imbedded in compact felspar, which in one or two instances is mingled with compact quartz.

It merits particular notice that the substance of each cross course (viz. quartz) uniformly traversed the channel of elvan, but, while in it was much smaller and more compact than when in the schist.