The experiments described in this paper were suggested to me many years ago, when employed in studying the Geological System of the late Dr Hutton, by the following plausible objection, to which it seems liable.Granite, porphyry, and basaltes, are supposed by Dr Hutton to have flowed in a state of perfect fusion into their present position; but their internal structure, being universally rough and stony, appears to contradict this hypothesis; for the result of the fusion of earthy substances, hitherto observed in our experiments, either is glass, or possesses, in some degree, the vitreous character.