527. As no earth is in its totality corrosive, and none such occurs in nature or has at least not been originally produced from it, so may the insolubility of the earths in water be set up as an essential and thoroughly valid characteristic of the earths. Their distinctive characters have been sedulously rendered fluctuating, by having been drawn not from nature, but the products of art. That the corrosive chalk is soluble in water, and may therefore be a salt is true; but it has not issued thus out of the womb of nature. Mineralogy knows nothing of a corrosive calcareous earth. The earths are sufficiently separated from the salts by their insolubility in water. They are separated from the ores by their incombustibleness, or, if they have been already burnt, by their incapacity for reduction. As both of these qualities are imparted by fire, so the earths are distinguished by their immutability in fire, whereby is naturally understood not the scoriation, but change of the earthy character. They differ also in the same manner from the Inflammables. Nature does not undertake the artificial reductions of earths to Metalloids, at least not so, that they may become again of themselves earths. The metals are permanent reductions. 528. Earth is thus the body, which is mutable neither in water, air, nor fire. _Earth is a water-, air-, and fire-proof body._ This is the brief, rigid, wholly exclusive, and significantly expressive definition, which a so-called empirical science could never, but philosophy alone, bestow. 529. The Ore is not soluble in water, nor mutable in air; on the contrary, it is fusible, oxydizable, or reducible in fire. _Ore is a water-and air-, but not fire-proof body._ 530. The Inflammable is immutable in water, but mutable in air and fire. _The Inflammable is a water-proof, but not air-and fire-proof body._ 531. The Salt is soluble in water, and decomposible in fire, but immutable in air. _Salt is an air-, but not water-and fire-proof body._ The legitimate series of gradations comprised in the above four definitions cannot escape the attentive reader, nor moreover that the properties of the earths are all affirmative. Nature has not employed such insignificant means of distinction as our mineralogy has done; has nowhere used an acid in order to distinguish the metals from the earths, nor savour to separate the salts from the earths; but she selects universal reagents which are the elements themselves. So simple is Nature, if we do not violate her by art. DIVISION OF THE EARTHS.