It does not often happen that the processes of the miner lead to so much geological discovery as might be expected; the works he undertakes follow the course of the vein he is exploring, or are confined within a small space bordering upon it. As the veins are sought after in but very few varieties of rock, so the number that are laid open to view is generally limited compared with those that exist in mining districts.
A tunnel of such an extent as the one now to be described, in such a district, crossing the direction of the metalliferous veins, and passing at such a depth under the surface, could hardly fail of proving an interesting object to the geologist as well as the miner.
Two facts have been ascertained by its progress:
1st, Relative to the rocks, that the killas of which the hill is mainly formed, is traversed by beds of other rock, whose direction is inclined to that of the metalliferous veins, and which have a pretty uniform dip or underlay to the north.
2d, Relative to the metallic veins or lodes, that they traverse all the strata, and that they have a remarkable difference in their dip or underlay on the two sides of the hill. Those on the north side dipping to the north, and those on the south side to the south.[1]
Commencing at the north end of the tunnel, I shall proceed to detail the strata that have been passed through, referring to the section accompanying this paper to shew their position, and to the specimens of the rocks themselves which I have selected to exhibit their character.
- ↑ Since the paper was written it has been ascertained, as I have been informed, that some veins lately discovered in the space between Renfrews shaft and Brays shaft underlie to the south, which is an exception to the preceding observation. But it may be observed that this deviation takes place near the centre of the hill.
