Now, this being established, and the fluidity of the veins, when they penetrated into the schistus, being obvious, it necessarily follows, that the whole granite mass was also fluid at the same time. But this can have been brought about only by subterraneous heat, which also impelled the melted matter against the superincumbent strata, with such force as to raise them from their place, and to give them that highly inclined position in which they are still supported by the granite, after its fluidity has ceased. Thus a conclusion, rendered probable by the crystallization of granite, is established beyond all contradiction by the phenomena of granitic veins.[28] [Footnote 28: NOTE XV.] 83. With the granite, we shall consider the proof of the igneous origin of all mineral substances as completed. These substances, therefore, whether stratified or unstratified, owe their consolidation to the same cause, though acting with different degrees of energy. The stratified have been in general only softened or penetrated by melted matter, whereas the unstratified have been reduced into perfect fusion. 84. In this general conclusion we may distinguish two parts, which, in their degree of certainty, differ perhaps somewhat from one another. The first of these, and that which stands highest in point of evidence, consists of two propositions; namely, that the fluidity which preceded the consolidation of mineral substances was SIMPLE, that is, it did not arise from the combination of these substances with any solvent; and, next, that after consolidation, these bodies have been raised up by an expansive force acting from below, and have by that means been brought into their present situation. These two propositions seem to me to be supported by all the evidence that is necessary to constitute the most perfect demonstration. 85. The other part of the general conclusion, that fire, or more properly heat, was the cause of the fluidity of these mineral bodies, and also of their subsequent elevation, is not perhaps to be considered as a truth so fully demonstrated as the two preceding propositions; it is, no doubt, a matter of THEORY; or a portion of one of those invisible chains by which men seek to connect in the mind the state of nature that is present, with the states of it that are past; and participates of that uncertainty from which our reasonings concerning such causes as are not direct objects of perception, are hardly ever exempted. That it participates of this uncertainty in a very slight degree, will, however, be admitted, when it is considered that the cause assigned has been proved sufficient for the effect; that the same is not true of any other known cause; and that this theory accounts, with singular simplicity and precision, for a system of facts so various and complex, as that which is presented by the natural history of the globe.