Page:Transactions of the Geological Society, 1st series, vol. 3.djvu/266

 the engine and bye pits, which are the nearest to the fault, the same bed is 27 feet thick. The actual junction of the greenstone of the bed with that of the fault has not indeed been proved, but from the very little unexplored space at present between them, there can exist but little doubt I imagine as to the fact. Now, though it is possible that the outburst of the greenstone (supposing it to be really a bed) may so coincide with the elevation and curvature of the ridge as, with a thickness of no more than about 80 feet, to give the appearance of a rock 60 or 100 yards across, yet this hypothesis is scarcely consistent with the rapid increase of the angle at which the strata above the greenstone bed are elevated in the vicinity of the green rock fault, advancing in a few yards from 6° to 25°. The absence of the greenstone bed in the pit D. though it is full as near the line of bearing of the fault as the engine and bye pits are, is a further support of the opinion that I have hazarded. Upon the whole, then, I am inclined to consider the green rock fault as a fissure in the coal field, filled up by greenstone, and the supposed greenstone bed as a wedge-shaped prolongation of the same.

With regard to the mode in which this and similar fissures have been filled, whether by deposition of the constituents of greenstone from solution or suspension in a superincumbent aqueous fluid, or by the bursting from below upwards of earthy matter, either melted or in the state of boiling hot mud, like the mud-volcanoes of Mexico and of the island of Taman in the sea of Asof, I shall not pretend to decide.