7 8 Calcareous Genus. According to Mr. Lavoifier *, 100 parts chalk contain 52,603 of pure lime, 31,949 of fixed air, and 15,402 of water; but this large proportion of water is barely inferred from the quantity ab- forbed and retained by quick lime in a heat of 6oo° Fahr, and which he luppofes muß alfo be contained in chalk, a fuppofition that feems to me inadmiffible, as lime certainly has a üronger affinity to water, and retains rnore of it than aerated calx has, or can retain. Befides, by his own firft experiment, 1404 grains of chalk lofe by folution in nitrous acid 576 grains, that is, at the rate of 41.025 per ct. which is farther con- firmed by the quantity of air given out in that experiment, viz. öoo French cubic inches in the temperature of between 16 0 or 17 0 of Reaumur, barometer at 28 French inches nearly. Now by his own rules of reduction, 800 cubic inches, at the temperature of 16 0 , 5 Reaumur, would make but 775,24 cubic inches at io° of Reaumur, and thefe would weigh by his rule of eftimation 552, 88 grains, which amounts to 39,47 per ct. 3d Family. Arenaceous limeftone. Ganil. This is fo called from its brittlen'efs, and not from its containing fand. The colour of the fpecimens I have feen was yellowifh white. Lulfre 1, from a few lhining particles. Tranfpareiicy 1. 1 Laitoiiiar, 201. / In