The Silurian System, Founded on Geological Researches in the Counties of Salop, Hereford Etc (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1839 Excerpt: ... mines on the west. I have thus attempted to give a sketch of the manner in which this district is traversed by a variety of veins which are more or less productive of lead ore. In a plan of Mr. More's of Linley Hall, the chief proprietor in this district, upwards of twenty-four are laid down in the district of Shelve alone, excluding the tracts around the Bog and Penally; so that, comprehending the principal portion of the mining ground, we may say that it contains upwards of thirty metalliferous veins which have been profitably worked. Adding to these the numberless poor and small lead veins in the extremities of the district, and all those which although containing only sulphate of barytes, quartz, and lime, have been produced by the same causes as those which bear lead, we shall find there are few tracts of given extent in any part of the world which are veined to a greater extent. Whilst all the masses of trap rock, whether intrusive or interstratified, range parallel to the strike of the associated strata, viz. from N.N.E. to S.S.W., the metalliferous veins are in most cases transverse or oblique to such direction. In some instances, indeed, they are only very slightly oblique to the strike, as in the Roman vein, but in the great majority of instances they are more obtusely transverse to the prevailing direction of the strata, or radiate as it were across those beds of surrounding shale and sandstone which are contiguous to bosses of intrusive greenstone. In no instance, however, do they continue through the latter. At the same time they occa CONNECTION OF MINERAL VEINS WITH VOLCANIC ACTION. 283 sionally pass through some of the stratified volcanic grits which have been shown to be contemporaneous with the strata of the Lower Silurian rocks. VVi...