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, | | | | | | | | | | | | | 1275-95 | A | F | B |...|...|...|... |...|...|... |... | | Liber Ignium, _cir._ 1300 | A |...|...|...|...|...|... |...|...|... |... | | Whitehorne, 1560 | A | B | F | C | G | I | F´ | D | E | D´ | G´ | | Waltham Abbey, 1860. | A | B | C | D | E | F | G | 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. CHAPTER III THE GREEKS Homer knew nothing apparently of incendiary compositions. When the Trojans set fire to the Greek ships, he certainly says that they burned with “unquenchable flame” (ἀσβέστη φλόξ), _Iliad_, xvi. 123; but this is a mere figure of speech, for presently afterwards he tells us that Patroclus extinguished the fire (κατὰ δ’ ἔσβεσεν αἰθόμενον πῦρ), 293. The Assyrian bas-reliefs in the British Museum prove that liquid fire was used in warfare in very remote times. Whether the Greeks adopted its use from the Orientals or originated it themselves, there is little evidence to show; but traces of it are found at an early date, for instance at the siege of Syracuse,[44] 413 B.C., and the siege of Rhodes,[45] 304 B.C. Vessels full of burning matter were thrown, at first by hand, from walls and the tops of forts upon besiegers; and when shell of suitable construction had been devised, these missiles were discharged from machines.