This passage of Malachi was so understood in the oldest times. Professor Tychsen, a true pupil and intimate friend of Michaelis, to whose opinion I subjected my doubts, assured me that Michaelis was never able to convince him of the justness of his exposition; especially as Jerome[1239], without the least hesitation, understood borith to be a plant growing in Palestine, and used there for washing; and as the Greek translators, who were much nearer to the period of the poet, and could not be unacquainted with a thing so much used, have translated borith by the word ποα, a plant.
In Jeremiah, chap. ii. ver. 22[1240], both the substances formerly used for washing, nitrum and the soap-plant, are so clearly named, that Michaelis was obliged to admit that we cannot understand there soda or potash, but a ley or soap, the last of which however was not at that time known. But, to speak the truth, potash and soda would not be altogether unfit for washing; at any rate, not less fit than the nether or nitrum there named. What may serve, however, to refute entirely the opinion of Michaelis is, that no proof has yet been found that soda is of so great antiquity. For my part, I am acquainted with no older mention of it than that which occurs in the works of the more modern Arabian physicians, Avicenna, Serapio, and others[1241].
All these grounds afford sufficient proof that the nitrum of the ancients was our natrum, and not our saltpetre. But still, in the account given by the ancients of that salt, there remain many things inexplicable. Thus, for example, no one can accurately define the epithets, chalastricum, halmirhaga, agrium, spuma nitri, aphronitrum, and others, because they do not indicate different kinds, as already said, but accidental properties of the same salt. Without enlarging further on this subject, I shall only remark that Pliny admits a natural and an artificial kind of nitrum, and this division is adopted by Serapio; but the latter term has not the meaning which we affix to it at present. The ancients were acquainted with no other than native nitrum, which they called artificial only when it required a little more trouble and art to obtain it.
Most of the physicians recommend red nitrum, which is mentioned also by many of the modern travellers. When Prosper Alpinus was in Egypt the rose-red nitrum cost twice as much as the white. The red colour, in all probability, arises from a metallic admixture; yet the red nitrum may be purer than the other, as red or violet rock-salt is often clearer and purer than that which is colourless.
One of the darkest parts in the history of nitrum is the following passage of Pliny: “Faciunt ex his vasa, nec non frequenter liquatum cum sulphure, coquentes in carbonibus.” The latter words he seems soon after to repeat: “Sal nitrum sulphuri concoctum in lapidem vertitur.” From these words J. Rhodius[1242] concludes that nitrum fixum was at that time known, because he considered nitrum to be saltpetre; but in that case with the sulphur, Glaser’s sal polychrest must properly have been produced. This, however, was not the case, because nitrum was fixed alkali. The ancients therefore, when they placed it with sulphur in a crucible upon burning coals must have obtained liver of sulphur, which when it cools is hard, but soon becomes moist when exposed to the air. But I will not venture to determine whether anything of this kind is to be supposed in Pliny, who did not himself fully understand the subject on which he touches.
The account of vessels made of nitrum is still more singular. Michaelis conjectured[1243] that articles of various kinds were cut out of this substance, not for real use but merely for ornament, in the same manner as similar things are cut out of rock-salt in Transylvania, many specimens of which I have in my collection[1244]. But even if nitrum had been compact and strong enough for this purpose, there could not be the same inducement to employ it as rock-salt, which, in consequence of its solidity, transparency, brightness and smoothness, appears to be capable of furnishing vessels equal to those made of the most beautiful crystal. Dalechamp seems to explain the whole as applicable to glazing; but in this case nitrum could serve only as a flux.
Though it can be certainly proved that the nitrum of the ancients was an alkaline salt, it is difficult to determine the time when our saltpetre was discovered or made known. As many have conjectured that it was a component part of the Greek fire, invented about the year 678, which, in all probability, gave rise to the invention of gunpowder, I examined the prescriptions for the preparation of it. The oldest, and perhaps the most certain, is that given by the princess Anna Comnena; in which however I find only resin, sulphur and oil, but not saltpetre. Klingenstierna[1245] therefore judged very properly, that all recipes in which saltpetre occurs are either forged or of modern invention. Of this kind are those which Scaliger, at least according to his own account, found in Arabic works, and in which mention is made of oleum de nitro and sal petræ[1246]. But it does not occur in that prescription given by Marcus Græcus, and copied by Albertus Magnus, who died in 1280[1247].
I must still believe that the first certain mention of saltpetre will be found in the oldest account of the preparation of gunpowder, which, in my opinion, became known in Europe in the thirteenth century, about the same time that the use of the Greek fire, of which there were many kinds, began to be lost. Among the oldest information on this subject is that found in the above-quoted work of Albertus Magnus, and the writings of Roger Bacon, who died in 1278. It is doubted whether the first-mentioned treatise belongs to Albertus; but it is certain that the author, whoever he may have been, and also Bacon, both derived their information from the same source.
When M. von Arretin lately announced that he was about to publish a manuscript preserved in the electoral library at Munich, which contained the true recipe for making the Greek fire and the oldest for gunpowder, the same writing, as appears, was printed from two manuscripts in the library at Paris. I have now before me a copy of it, which was transmitted to the library of our university by M. Laporte Dutheil, conservateur des Manuscrits de la Bibliothèque[1248].
It contains many recipes, but only with a few variations, as in Albertus Magnus; and it may be evidently seen that Roger Bacon employed this writing, which is mentioned by Jebb in the preface to his edition, from a copy preserved in the library of Dr. Mead. Of this Marcus Græcus nothing at present is known. According to some, he lived in the ninth century; but others, with more probability, place him in the thirteenth. Of his work, perhaps, we have only a translation; for, from the surname Græcus, there is reason to think that the original was written in the Greek language. I must, however, remark that Cardan, where he gives directions for making a fire which can be kindled by water, names Marcus Gracchus, but not Græcus. Scaliger, who, as is very probable, had this writing also, makes no mention of it or its author.