The laws which regulate the deposition of lead ore in veins; illustrated by an examination of geological structure of the mining districts of Alston Moor . med when the strata were less consolidated and of a moreuniform consistency. If this supposition be correct, it will fur-nish an additional argument in favour of the priority of theirformation to that of the east and west veins. Below the GreatLimestone the cross veins have less hade in the hard strata oflimestone and sandstone, and their other appearances likewiseconform more to those of the east and west veins. The intersections of veins
The laws which regulate the deposition of lead ore in veins; illustrated by an examination of geological structure of the mining districts of Alston Moor . med when the strata were less consolidated and of a moreuniform consistency. If this supposition be correct, it will fur-nish an additional argument in favour of the priority of theirformation to that of the east and west veins. Below the GreatLimestone the cross veins have less hade in the hard strata oflimestone and sandstone, and their other appearances likewiseconform more to those of the east and west veins. The intersections of veins of this douky and impervious cha-racter with east and west veins, can only be considered as un-favourable to a free circulation of water in the open spaces of thelatter as shown in Plate X. But when the cross veins are weak,the obstruction would probably be very slight, especially if theeast and west veins are of later date. The inclination of the stratavaries more near strong cross veins than when near east and ^Icf^Je. Seii^ PLATE a. mqhaalSili\laiCocdSili lyreatl,\me.! I i t|. ^ BELOW THE EAETHS SURFACE. 119 west veins; and, in accordance with the third law, such incli-nation would either promote a free circulation of water near thesurface, or otherwise retard it, and cause it to penetrate togreater depths. The throws of the cross veins are often veryconsiderable, and this circumstance must necessarily have greatinfluence towards promoting as well as preventing,—as the casemay be,—the descent of water into any particular stratum. Itis evident that the Great Limestone, or any other stratum ofhard rock, lying at moderate depths from the surface, andhaving an inclination to its outcroppiag, is placed in a morefavourable position for water percolating, and also for circulat-ing ia a longitudinal direction, than the same stratum throwndown 100 or 200 feet, on that side nearest the water shed of themountain, as shown in Plate XII. The dyke of clayey mattercontained i
Size: 979px × 2553px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1860, booksubjectgeology, bookyear1861
