Page:Transactions of the Geological Society, 1st series, vol. 3.djvu/86

 situations. They are to be observed pretty frequently passing through the rock at Coruisk, and through the greenstone and clinkstone of Garsven, in the neighbourhood of which latter they abound. Their compactness and lustre are frequently so great that they approach in appearance to that pitchstone which forms the basis of the beautiful columnar porphyry of Egg. In addition to this feature they are strongly distinguished from the trap veins that traverse the sandstone by the intimate and almost inseparable union which they form with the body of the rocks which they traverse, whereas the latter are separated with the greatest ease.

There is still another set of veins found in this place, which however even and compact they may appear on a fresh fracture, and thus resembling basalt, appear to consist of clinkstone. This may be concluded from the facility with which they decompose at the surface into a greyish or whitish earthy looking substance, and from the depth of that decomposition. They are further distinguished by the frequency and minuteness of their ramifications, which are often drawn out to the size of a thread. Veins of this description have not as far as I know, been noticed, but they are not uncommon in the western islands, and they abound particularly in some parts of the Long isle; in this place they are chiefly seen on the borders of the small and picturesque lake Coruisk, and are found traversing the hypersthene rock, as well as the veins themselves, which consist of this mineral.

Having now described the trap veins which pass through the mountain trap, and those, perhaps more important ones as far as relates to that rock, which do not pass through it, I must turn the reader's attention to those which are found in the stratified trap. These are not very abundant, but may be seen distinctly among other places on the western shore, traversing the lofty cliffs in various