When these concretic juices issue immediately from marble and hard stone, the lapidific matter conveyed by the water being rather dissolved than loosened, the small constituent parts take a regular figure, and form columns, terminated by triangular points, which are transparent and consist of oblique strata; this is called Spar, or Spall. It is generally transparent and colourless, but when the stone or marble, from whence it issues, contains metallic parts, this spar is as hard as stone; it dissolves, like stone, by acid spirits, and calcines with the same heat; therefore we cannot doubt that it is real stone, and perfectly homogeneous. It might even be said that it is a pure and elementary stone, under its proper and specific form. Most naturalists nevertheless look on this matter as a direct substance, existing independent of stone; it is the lapidific or crystalline juice which, according to them, not only binds the parts of common stone, but even those of flint. This juice, say they, constantly augments the density of stones by reiterated filtrations, and at length converts them into real flint. When this juice is fixed in spar, it continues to receive still more pure juices, which increase its density and hardness, so that this matter successively becomes glass, then crystal, and at last a perfect diamond. But if this is true, why, in whole provinces, does this crystalline juice form only stone, and in others nothing but flint? Will they say, that the two soils are not of a like age, and that this juice has not had time to circulate and complete the end of its natural action? This is not probable. Besides, from whence does this juice proceed? If it produces stone and flints, what is it that produces this juice? It is apparent that it has no existence independent of these matters, which of themselves can give to the water that penetrates them a petrifying quality, always relative to their native and specific character; insomuch that when it filtrates through stones it forms spar, and when it issues from flints, crystal: and there are as many different kinds of this juice, as matters from which they proceed. Experience perfectly agrees with this idea. The waters which filtrate through stone quarries, generally form soft and calcinable matters like the stones themselves; on the contrary, those which spring from rock and flint form hard and vitrifiable congelations, which have all the other properties of flint, as the first have all those of stone; so the waters which have penetrated the beds of mineral and metallic substances produce pyrites, marcasites, and grains. We have observed, that we might divide all matters into two great classes, vitrifiable and calcinable; clay and flint, marle and stone, may be looked upon as the two extremes of each of these classes, the intervals of which are filled with an almost infinite variety of the mixt matters that have always one or other of these substances for their basis.