Page:Transactions of the Geological Society, 1st series, vol. 2.djvu/422

From Wikisource
Jump to navigation Jump to search
This page has been validated.
Dr. Mac Culloch on the Geology of

merely nugatory, but injurious to correct observation, chaining down our conclusions in an obedience to particular dogmas, and producing impediments destructive to the progress of legitimate science.

Another tract of limestone, of a distinct character, occurs in the same valley, occupying a position nearly parallel, at some distance from it. Of this I have unfortunately nothing to record beyond the detail of specimens. The whole inclination of the hill on this side of the valley is covered with a deep bed of soil, such as to render it impossible to trace the position of the rock, of which, all that is visible appears in the form of detached masses, apparently without order or semblance of stratification, rising through the grass. The rock itself is an object worthy of attention from its œconomical qualities, affording various specimens of marble, of a colour from pure white to grey, which have already been introduced into commerce, and for which a premium has been assigned to Mr. Joplin, of Gateshead, from the Society of Arts. It is the same marble described by Williams. The principal varieties are the following:

  1. Pure white of a milky opaque aspect, with a crystalline texture, and large grained granular fracture, approaching to the splintery. Acquires a smooth surface on the polisher, but remains of a dead hue like the marble of Iona, reflecting no light. Hence its uses as an ornamental marble are much circumscribed.
  2. White mottled with gray, of a large platy fracture, and capable of receiving a high polish, forming a marble of some beauty.
  3. Highly crystalline and translucent, with a large platy fracture, and of a gray colour, capable of being applied to the purposes of ornament in sepulchral sculpture.