[369] “The mother liquid, from which the saltpetre flour has been deposited, is boiled down and crystallised.”—Bloxam’s “Chemistry,” 8th ed., p. 488.
[370] Salit petræ is the reading of Zetzner’s Theatrum Chemicum, 1613, v. 962, which is adopted by Reinaud and Favé, p. 123; of Manget’s Bibliotheca Chemica, 1702, i. 624; of the Verosimilia Sacra et Profana of Hoven and Molfenger, 1732, ii. 93; and of the copy used by Romocki, i. 93. Prof. Brewer’s MS. reads sal petræ.
[371] “Atque mala vites incidere falce novellas.”—Vergil, “Bucol.,” iii. 11. The word, however, may be simply novæ.
[372] “Maltha, quæ est genus bitumenis.”—Opus Majus, London, 1733, p. 474.
[373] “Possumus artificialiter componere ignem comburentem, scilicet, ex sale petræ ... ex oleo petroleo ... ex maltha et naphta et consimilibus.... His vicinus est ignis græcus et multa comburentia.”—De Secretis, cap. vi.
[374] “Maltha ... projecta super hominem armatum comburit eum.... Ignis comburens fit ex eo qui cum difficultate potest extingui, nam aqua non extinguit.”—Op. Maj., as above.
[375] “Sunt alia stupenda naturæ. Nam soni velut tonitrua et coruscationes fieri possunt in aere; imo majori horrore quam illa quæ fiunt per naturam. Nam modica materia adaptata, scilicet ad quantitatem unius pollicis, sonum facit horribilem et coruscationem ostendit vehementem.”—De Secretis, cap. vi.
[376] See p. 156.
[377] “Quaedam vero auditum perturbant.... Nullus tonitrui fragor posset talibus comparari. Quædam tantum terrorem visui incutiunt, quod coruscationes nubium longe minus et sine comparatione perturbant.... Experimentum hujus rei capimus ex hoc ludicro puerili, quod fit in multis mundi partibus, scilicet ut instrumento facto ad quantitatem pollicis humani ex violentia illius salis qui sal petrae vocatur, tam horribilis sonus nascitur in ruptura tam modicæ rei, scilicet modici pergameni, quod fortis tonitrui sentiatur excedere rugitum, et coruscationem maximam sui luminis jubar excedit.”—Opus Majus, London, 1733, p. 474. “Offenbar ist hier das Schiesspulver verstanden.”—L. Schneider, “Roger Bacon,” 1873, p. 110. Two centuries before, when referring to Bacon’s remarks on the destruction of the Midianites by Gideon, Borrichius had said: “Hic apertissime loquitur Bacon de nitrato illo sclopetorum pulvere.”—De Ortu &c., Chemiæ, 1668, p. 126.
[378] This is M. Berthelot’s view; Sur la Force des Matières Explosives, Paris, 1883, ii. 358; and it is probably the right one.