Page:Transactions of the Geological Society, 1st series, vol. 4.djvu/404



The inspection of the drawing will show more readily than any description, that the vein consists of a series of separate fragments, having somewhat of a general parallelism, with a correspondence at any two neighbouring extremities, such, as to render it a matter past doubt that they have once formed a continuous line. To displace such a vein into its present position must have required a series of slides or shifts, each advancing by nearly a similar space beyond the one preceding it. But this sort of echellon movement will be very visible in an outline or diagram in which I have attempted to replace the vein in its original position, and also to trace the alignement on which each part must have moved to its present place.



The deficiency of parallelism occurring in this diagram arises from my having intentionally left the replaced ends at a small distance, that their correspondence might be more visible.

There is now no appearance of slide or fissure, or discontinuity of any sort in the mass, but the texture of the whole is uniform and continuous. As the specimen has been completely and highly polished, there can be no doubt respecting the accuracy of this observation. It may afford matter for speculation to inquire in what condition the rock must have been to have undergone this change. It has probably consisted originally of a series of thin strata, which having been at some subsequent period fissured at an angle, have admitted the infiltration of the white carbonat of lime which now constitutes the vein in question. That it was perfectly hard at the time of this change the angularity of the fragments shows. The same solution which filled the vein has probably joined the laminæ, and cemented the whole once more into a solid mass, although the junctions are no longer visible.