183. A very remarkable fact of this kind occurred not long ago, in digging the Huddersfield canal in Yorkshire; and a very distinct account of it is given in the _Philosophical Transactions_, by the engineer who directed the work. In carrying a tunnel into the heart of a hill, the miners came to what is called in the description a _fault_, _throw_, or _break_, or what we have here called a shift, which was filled with _shale_ set on edge, mixed with softer earth, and in some places with small lumps of coal. The fault or space filled with these materials, was in general about four yards broad, and lay nearly in the direction of the tunnel, so that a considerable extent of it was visible. Beside the shale, it contained a _rib_ of limestone, about four feet thick, which run parallel to the sides of the _fault_, and about four feet from the southern margin of it. On each side of this rib were found balls of limestone, promiscuously scattered, and of various sizes, from an ounce to one hundred pounds weight. The balls, when broken, were found to contain some pyrites near their edges; they were not perfectly globular, but flattened on the opposite sides, and similar to one another.[92] At the time when the account was written, about seventy yards of the rib had been discovered. [Footnote 92: Phil. Trans. 1796, p. 350.] 184. Now, it is certain, that neither this rib of limestone, nor the balls that accompanied it, can have come from above, as there is no limestone within twenty miles of the place where they were found. They must, therefore, have been forced up from below, and no doubt belong to some limestone strata, which lie there at a great depth under the surface. The length of this fragment of rock, which, from the account, one must suppose to have been entire, conveys no mean idea, either of the intensity or regularity of the force by which it was brought into its present situation. In veins, it is not uncommon to meet with stones that appear to have come from a greater depth: but this is probably the most remarkable instance of the same phenomenon, which has appeared in a mere slip, and none, I think, can speak a language less liable to be misunderstood. 185. I shall here mention another mark of violent fracture, that has been observed in rocks of breccia or pudding-stone, which, though not of the same kind with the preceding, and of a nature quite peculiar, belongs rather to this place than any other. In rocks of the kind, just mentioned, it sometimes happens, that considerable portions are separated from one another, as if by a mathematical plane, which had cut right across all the quartzy pebbles in its way. None of the pebbles are drawn out of their sockets, that is, out of the cement that surrounds them, but are divided in two with a very smooth and even fracture. The pebbles, in the instances which I have seen, were of quartz, and other species of primary and much indurated rock.