a Elements of Mineralogy, PART I. Of Earths and Stones. The term earth denotes a taftelefs, inodorous, drv, brittle, uninflammable, l'ubftance whofe fpecific gravity does not exceed 4,9, and gives no tinge to borax in fufion. Yet quicklime is ufually called an earth, though it has a ptingent tafte, and is very perceptibly foluble in water, and fome forts lately dilcovered in very confide- rable proportion: fo alfo is Gypfum, which is allo in fome degree lbluble in water, and even contains a faline principle : perhaps, in ftrifinefs, there is no earth which is not in fome degree foluble. However, fince a line muft Be drawn between falts and earths, I think it fliould bcgin , where folution is fcarcely perceptible ; falts ter- minating, and earths, in ftrictnefs, commcncing, where the weight of water requifite for the folu tion exceeds that of the lolvend 1000 times. But, not to depart too widely from the commonly received import of words that are in conftant ufe, fubftances that require xco times their weight of water to difl’olve them, and have the other fen- fible appearances of earths, may be fo ftyled in a loofe and populär fenfe. Stones differ from earths principally in cohefioti and hardnefs, and therefore are included under the fame general name: yet diamond' is alfo called a ftone, though it probably contains no earth of any kind. Mo«