Extract

The shifting of veins on a small scale is much more common than the larger phenomena of this nature, which are nevertheless of frequent occurrence wherever veins exist. These larger dislocations are known to arise either from the lateral motion or subsidence of the containing parts, the sides of the line of fracture sometimes remaining in contact, and being at others separated by a vein of another description, too well known among miners to need any comment here. I know not why mineralogists have sometimes imagined that such appearances were in the smaller examples fallacious, and were contemporaneous with the formation of the containing stone. The vein represented in the accompanying drawings is at any rate too remarkable to admit of such an explanation, and its character is sufficiently decided to establish a general rule in favour of all similar appearances.

The rock in which this shifted vein is contained is a secondary limestone, and was brought from Ireland. The specimen, which formed a mill-stone of six feet in diameter, belongs to the Royal Powder Works at Waltham Abbey.

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,