Page:Transactions of the Geological Society, 1st series, vol. 2.djvu/443

Rh constitute them, and that the language of Nature is often as intelligibly spoken in the minute space of an inch, as in the immensity of a mountain. It is scarcely necessary to add, that the other prevailing theory, that of aqueous formation, supposes the substances which constitute this rock to have been crystallized from a watery solution, and that the fundamental objection to the igneous explanation, is the apparently chemical impossibility, that of a rock compounded of two crystallized substances, the one which is fusible at the lowest temperature, and therefore would be the last to crystallize, should by crystallizing first, have made its impression on the other. An analogy has, I know, been offered in explanation of this difficulty, but it will immediately be seen that it is at least incompetent to explain the particular case under review.

The first specimen which I have to describe is a detached crystal of a flattened and irregular figure. It has been broken into four parts, by transverse fractures, which have again united without the intervention of any intermediate substance. Previous to this reunion however, they have all been slightly shifted, in such a way that the several parts of the fractures project, and the whole crystal has undergone a slight deviation from its original straight line. If it be alledged that this appearance could arise from a disturbed crystallization, the next specimens will remove any doubt on this head.

In these, the crystals have not only been fractured in the same way, across their axes, but the fractures are filled by the quartz and felspar which constitute the body of the rock. The granite veins of Arran do not show more clearly the ramification of a central substance through the fractures of the neighbouring rock, than these specimens show the veins of quartz proceeding from the mass, and penetrating every fissure which had been formed in the

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