Theory of the Earth

3dly, THAT the contained substances must have been in a fluid state, in order to their crystallizing.

Lastly, THAT as this fluid state had not been the effect of solution in a menstruum, it must have been fluidity from heat and fusion.

THERE are in jaspers and agates many other appearances, from whence this last conclusion may be formed with great certainty and precision; but it is hoped, that what has been now given may suffice for establishing that proposition without any doubt.

IT must not here be objected, that there are frequently found siliceous crystals and amethysts containing water; and that it is impossible to confine water even in melted glass. It is true, that here, at the surface of the earth, melted glass cannot, in ordinary circumstances, be made to receive and inclose condensed water; but let us only suppose a sufficient degree of compression in the body of melted glass, and we can easily imagine it to receive and confine water, as well as any other substance. But if, even in our operations, water, by means of compression, may be made to endure the heat of red hot iron without being converted into vapour, what may not the power of nature be able to perform? The place of mineral operations is not on the surface of the earth; and we are not to limit nature with our imbecility, or estimate the powers of nature by the measure of our own.

TO conclude this long chemico-mineral disquisition, I have specimens in which the mixture of calcareous, siliceous and metallic substances, in almost every species of concretion which is to be found in mineral bodies, may be observed, and in which there is exhibited, in miniature, almost every species of mineral transaction, which, in nature, is found upon a scale of grandeur and magnificence. They are nodules contained in the whinstone, porphyry, or basaltes of the Calton-hill, by Edinburgh; a body which is to be afterwards examined,

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