Page:A Treatise on Geology, volume 2.djvu/191

 CHAP. VIII. separated portions of the veins which they divide and dislocate.

There is, perhaps, no portion of geological science less satisfactory than the variety of opinions, and conjectures, which, till within a few years, constituted what was called the "Theory" of mineral veins. In no department of geology is it so difficult to observe accurately the phenomena which form the basis of reasoning, or to obtain from experience the data which ought to limit and direct speculation. A short inspection of a mine, with the disadvantage of confused lights and noises, and explanations hid in a phraseology of very difficult interpretation, leaves on the mind a feeling of disquieting disappointment. The important facts of the intersection of veins are not seen; the segregations of ore in a vein, the change of the contents with the change of ground, with the depth, the underlie, and other influential conditions, must all be taken on the affirmation of the agent, in whose office the stranger expects in vain to find a complete record of the subterranean operations, with all the scientific data which they have revealed. Dr. Boase was so impressed with these difficulties, that in his examination of the veins of Cornwall, with a view to understand their formation, he declined to enter the mines at all, preferring to trust his reasonings on the few phenomena in the sea cliffs, which he could accurately examine, than on the almost innumerable facts which the mining art has disclosed, only to be, in many cases, lost for ever to science. The want of a national system of mining records is now acknowledged, and ought to be remedied. Werner's views on this subject are not unworthy of his high reputation. (See his work "On the Origin of Veins.")