The original is as follows:—

Calcem diligenter purifica, ut fiat terra pura penitus liberata ab aliis elementis. Dissolvatur in aqua cum igne levi, ut decoquatur quatenus separetur pinguedo sua, donec purgatur et dealbetur. Iteretur distillatio donec rectificetur: rectificationis novissima signa sunt candor et crystallina serenitas. Ex hac aqua materia congelatur. Lapis vero Aristotelis, qui non est lapis, ponitur in pyramide in loco calido.

Accipe lapidem et calcina ipsum. In fine parum commisce de aqua dulci; et medicinam laxativam compone de duabus rebus quarum proportio melior est in sesquialtera proportione. Resolve ad ignem et mollius calefac. Mixto ex Phœnice adjunge, et incorpora per fortem motum; cui si liquor calidus adhibeatur, habebis propositum ultimum. Evacuato quod bonum est. Regyra cum pistillo, et congrega materiam ut potes, et aquam separa paulatim.[43]

TABLE I.

Methods of Refining Saltpetre.

Roger Bacon, cir. 1248 A B F C G H ... ... ... ... ...
Hassan er-Rammah, 1275-95AFB........................
Liber Ignium, cir. 1300 A .................. ............
Whitehorne, 1560 A B F C G I F´ D E D´ G´
Waltham Abbey, 1860. A B CDEFG H I ... ...

A = Preparation of grough from natural saltpetre.
B = Boiling the solution of grough saltpetre.
C = Removal of insoluble impurities.
D = Second boiling of the solution.
E = Filtration.
F = Use of wood-ash, animal charcoal, &c.
G = Crystallisation.
H = Stirring the depositing solution.
I = Washing and drying.

The simple and highly probable conclusion to be drawn from the foregoing facts is, that saltpetre was not discovered until the second quarter of the thirteenth century; but this conclusion is not universally accepted. It is said by some that although saltpetre was unknown to the rest of the world until then, it had been secretly used by the Greeks for five hundred years. This theory will be examined in the following chapter.