[Note 6: The Chevalier de Dolomieu has imagined an ingenious theory for the solution of siliceous substances in water [Journal de Physique, Mai 1792.]. This theory has not been taken up merely at a venture, but is founded upon very accurate and interesting chemical experiments. Hitherto, however, the nature of the siliceous substance is not sufficiently known, to enable us to found, upon chemical principles, the mineral operations of nature. That siliceous substance may be dissolved, or rendered soluble in water, by means of alkaline salt, and that it may be also volatilised by means of the fluor acid, is almost all that we know upon the subject. But this is saying no more in relation to the mineral operations employed upon the siliceous substance, than it would be, in relation to those upon gold, to say that this metal is dissolved by aqua regia. It is to be admitted, that every simple substance may have its menstruum, by means of which it may be retained with water in a dissolved state; but from this it does not follow, that it is by the means of aqueous solutions of all those mineral bodies, that nature operates the consolidation of bodies, which we find actually accomplished with all those different substances. It is the business of this work to show, that from all appearances in the mineral regions, as well as those upon the surface in the atmosphere, the supposition, of that manner of consolidating bodies by solution, is inconsistent both with natural appearances, and also with chemical principles. Our ingenious author, who has, with, great diligence as well as an enlightened mind, observed the operations of nature upon the surface of the earth, here says, "ce n'est pas sans étonnement que je remarque depuis long-temps que jamais aucune eau qui coule à la surface de la terre n'attaque le quartz, aucune n'en tient en dissolution, pendant que celles qui circulent intérieurement le corrodent aussi souvent qu'elles le déposent."--How dangerous it is in science for ingenious men to allow themselves to form conclusions, which the principles on which they reason do not strictly warrant, we have a remarkable example in the present case.