[1193] More accounts of native saltpetre may be found in Recueil de Mémoires sur la Formation du Salpetre. Par les Commissaires de l’Academie. Paris, 1776, 8vo. Del Nitro Minerale Memoria dell’ ab. Fortis, 1787, 8vo.
[1194] The first, or one of the first, who was acquainted with and made known the cubic saltpetre, was professor John Bohn of Leipsic, in the Acta Eruditorum, 1683, p. 410; but with more precision in his Dissertat. Chymico-Physicæ, Lips. 1696, 8vo, p. 36.
[1195] [It is scarcely necessary to inform the reader that the author understands the soda of commerce, which is a carbonate of soda, and not the hydrated or caustic soda of chemists.]
[1196] [Crude soda or kelp was formerly manufactured to a very large extent in the Highlands, by burning the sea-weed, but since the tax has been taken off salt, most of the soda of British commerce is made by decomposing this with chalk and some carbonaceous matter.]
[1197] In like manner, a heap of dung covered with earth is lixiviated, and the result, without the addition of ashes, used as saltpetre.
[1198] The passage of Jerome relating to Proverbs, xxv. 20, I here insert entire, because I shall often have occasion to employ it:—“Nitrum a Nitria provincia, ubi maxime nasci solet, nomen accepit. Nee multum a salis Ammoniaci specie distat. Nam sicut salem in litore maris fervor solis conficit, durando in petram aquas marinas, quas major vis ventorum, vel ipsius maris fervor in litoris ulteriora projecerit; ita in Nitria, ubi æstate pluviæ prolixiores tellurem infundunt, adest ardor sideris tantus, quod ipsas aquas pluviales per latitudinem arenarum concoquat in petram; salis quidem vel glaciei aspectui simillimam; sed nil gelidi rigoris, nil salsi saporis habentem, quæ tamen, juxta naturam salis, in caumate durare, et in nubilos, aere fluere ac liquefieri solet. Hanc indigenæ sumentes servant, et ubi opus extiterit, pro lomento utuntur. Unde Judæo peccanti dicit propheta Jeremias: Si laveris te nitro, et multiplicaveris tibi herbam borith, maculata es in iniquitate tua, dicit Dominus Deus. Crepitat autem in aqua quomodo calx viva; et ipsum quidem disperit, sed aquam lavationi habilem reddit; cujus natura cui sit apta figuræ, cernens Solomon ait: Acetum in nitro, qui cantat carmina cordi pessimo. Acetum quippe si mittatur in nitrum, protinus ebullit.”
[1199] Herodot. ii. cap. 86 et 87.
[1200] Histor. Ægypti Naturalis iii. 2. See also Forskäl Flora Ægyptiaco-Arabica, p. xlv.
[1201] [Duhamel proved soda to be distinct from potash in 1736, Marggraf confirmed it in 1758.]
[1202] Lib. xxxi. cap. 10.