The islands of Lipara and Strongyle, or, as they are called at present, Lipari and Stromboli, contained so great a quantity of this substance, that the duty on it brought a considerable revenue to the Romans[497]. At one period, Lipari carried on an exclusive trade in alum, and raised the price of it at pleasure; but in that island at present there are neither vitriol nor alum-works. Sardinia, Macedonia, and Spain, where alum was found formerly, still produce a salt known under that name[498].
When our alum became known, it was considered as a species of the ancient; and as it was purer, and more proper to be used on most occasions, the name of alum[499] was soon appropriated to it alone. The kinds of alum however known to the ancients, which were green vitriol, maintained a preference in medicine and for dyeing black; and on this account, these impure substances have been still retained in druggists’ shops under the name of misy, sory, &c. But a method was at length found out of procuring thence crystallized martial salts (salts of iron), which obtained the new name of vitriol. This appellation had its rise first in the eleventh or twelfth century; at least I know no writer older than Albertus Magnus by whom it is mentioned or used. Agricola conjectures that it was occasioned by the likeness which the crystals of vitriol had to glass. This is also the opinion of Vossius[500]; and it is very singular that Pliny says nearly the same thing; for he observes, speaking of blue vitriol, the only kind then known, that one might almost take it for glass[501].
By inquiring into the uses to which the ancients applied their alum, I find that it was sometimes employed to secure wooden buildings against fire. This remark I have here introduced to show that this idea, which in modern times has given occasion to many expensive experiments, is not new. Aulus Gellius[502] relates, from the works of an historian now lost, that Archelaus, one of the generals of Mithridates, washed over a wooden tower with a solution of alum, and by these means rendered it so much proof against fire, that all Sylla’s attempts to set it in flames proved abortive. Many have conjectured that the substance used for this purpose was neither vitriol nor our alum, but rather asbestos, which is often confounded with Atlas-vitriol[503]; and against this mistake cautions are to be found even in Theophrastus. But it may be asked, With what was the asbestos laid on? By what means were the threads, which are not soluble in water, made fast to the wood? How could a tower be covered with it? I am rather inclined to believe, that a strongly saturated solution of vitriol might have in some measure served to prevent the effects of the fire, at least as long as a thin coat of potters’ earth or flour-paste, which in the present age have been thought deserving of experiments attended with considerable expense. It does not however appear that the invention of Archelaus, which is still retained in some old books[504], has been often put in practice[505]; for writers on the art of war, such, for example, as Æneas, recommended vinegar to be washed over wood, in order to prevent its being destroyed by fire.
I shall now proceed to the history of our present alum, which was undoubtedly first made in the East. The period of the invention I cannot exactly determine, but I conclude with certainty that it is later than the twelfth century[506]; for John, the son of Serapion, who lived after Rhazes, was acquainted with no other alum than the impure vitriol of Dioscorides[507]. What made the new alum first and principally known was its beneficial use in the art of dyeing, in which it is employed for fixing as well as rendering brighter and more beautiful different colours. This art therefore the Europeans learned from the Orientals, who, even yet, though we have begun to apply chemistry to the improvement of dyeing, are in some respects superior to us, as is proved by the red of Adrianople, their silks and their Turkey leather. The Italians procured their first alum from the Levant, along with other materials for dyeing; but when these countries were taken possession of by the Turks, it grieved the Christians to be obliged to purchase these necessary articles from the common enemy, and bitter complaints on that subject may be seen in the works of various authors. In the course of time the Italians became acquainted with the art of boiling alum; for some of them had rented Turkish alum-works, and manufactured that salt on their own account. They at length found aluminous minerals in their own country, on which they made experiments. These having answered their expectations, they were soon brought into use; and this branch of trade declined afterwards so much in Turkey, that many of the alum-works there were abandoned.
We are told by many historians that the Europeans who first made alum in Italy learned their art, as Augustin Justinian says, at Rocca di Soria, or Rocca in Syria. Neither in books of geography nor in maps, however, can I find any place of this name in Syria. I at first conjectured that Rocca on the Euphrates might be here meant, but at present it appears to me more probable that it is Edessa, which is sometimes called Roha, Raha, Ruha, Orfa, and also Roccha, as has been expressly remarked by Niebuhr[508]. Edessa is indeed reckoned to be in Mesopotamia, but some centuries ago Syria perhaps was understood in a more extended sense. This much at least is certain, that minerals which indicate alum have been often observed by travellers in that neighbourhood.
It appears that the new alum was at first distinguished from the ancient vitriol by the denomination of Rocca, from which the French have made alun de roche, and some of the Germans rotzalaun[509]. Respecting the origin of this name very different conjectures have been formed. Some think it is derived from rocca, which in the Greek signifies a rock, because this salt is by boiling procured from a stone; and these translate the word alumen rupeum, from which the French name is formed[510]. Some are of opinion that alum obtained from alum-stone has been so called to distinguish it from that procured from schists, which is generally mixed with more iron than the former[511]; and others maintain that alum acquired the name of Rocca from the alum-rocks in the neighbourhood of Tolfa[512]. It is to be remarked, on the other hand, that Biringoccio, that expert Italian, confesses he does not know whence the name has arisen[513]. For my part I am inclined to adopt the opinion of Leibnitz, that alumen roccæ was that kind first procured from Rocca in Syria; and that this name was afterwards given to every good species of alum, as we at present call the purest Roman alum[514].
In the fifteenth century there were alum-works in the neighbourhood of Constantinople, from which John di Castro, of whom I shall have occasion to speak hereafter, learned his art. May not these alum-works be those visited by Bellon, and of which he has given an excellent description[515]? He names the place Cypsella or Chypsilar, and says that the alum in commerce is called alumen Lesbium, or di Metelin. The alum procured from Constantinople at present may perhaps be brought from the same spot; but I am not sufficiently acquainted with its situation to determine that point with certainty, for Büsching makes no mention of it. In some maps I find the names Ypsala and Chipsilar on the western side of the river Mariza, Maritz or Maricheh, which was the Hebrus of the ancients; in others stands the name Scapsiler on the west bank of the sea Bouron; and it is not improbable that these may be all derived from the old Scaptesyle or Scapta Hyla, where, according to the account of Theophrastus, Pliny and others, there were considerable mines.
Another alum-work, no less celebrated in the fifteenth century, was established near the city Phocæa Nova, at present called Foya Nova, not far from the mouth of the Hermus, in the neighbourhood of Smyrna. Of this work, Ducas, who had a house there, has given a particular description, from which we learn that in his time, that is under the reign of Michael Palæologus, it was farmed by Italians, who sold the produce of it to their countrymen, and to the Dutch, French, Spaniards, English, Arabs, Egyptians, and people of Syria. This author relates very minutely in what manner the alum was made, but that work has been long since abandoned[516]: alum however made in the neighbourhood is still exported from Smyrna[517]. It is much to be wished that ingenious travellers would examine the alum-works in Thrace, around Smyrna, and in Turkey in general, and give an accurate description of them according to the state in which they are at present[518].
The oldest alum-works in Europe were established about the middle of the fifteenth century, but where they were first erected cannot with certainty be ascertained; for it appears that several were set on foot in different places at the same period. Some affirm that the first alum made in Europe was manufactured in the island Ænaria, or Pithacusa, at present called Ischia, by a Genoese merchant, whom some name Bartholomew Perdix, and others Pernix. This man, who is praised on account of his ingenuity and attachment to the study of natural history, having often travelled through Syria, learned the method of boiling alum at Rocca; and on his return found alum-stones among the substances thrown up by the eruption of a volcano which had destroyed part of the island, and gave occasion to their being first employed in making that salt. Such is the account of respectable historians, Pontanus[519], Bizaro[520], Augustine Justinian[521], and Bottone[522], who wrote much later. Bizaro says that this happened in the year 1459, which agrees perfectly with the account of Pontanus; for he tells us that it was under the reign of Ferdinand I., natural son of Alphonsus, who ascended the throne in 1458. Besides, the earthquake, which had laid waste the island one hundred and sixty-three years before, took place in 1301, which makes the time of this invention to fall about the year 1464. So seems Bottone also to have reckoned, for he mentions expressly the year 1465.
The alum-work which is situated about an Italian mile northwest from Tolfa, and six from Civita Vecchia, in the territories of the Church, is by some Italian historians reckoned to have been the first. However this may be, it is certain that it is the oldest carried on at present. The founder of it was John di Castro, a son of the celebrated lawyer, Paul di Castro[523], who had an opportunity at Constantinople, where he traded in Italian cloths and sold dye-stuffs, of making himself acquainted with the method of boiling alum. He was there at the time when the city fell into the hands of the Turks; and after this unfortunate event, by which he lost all his property, he returned to his own country. Pursuing there his researches in natural history, he found in the neighbourhood of Tolfa a plant which he had observed growing in great abundance in the aluminous districts of Asia: from this he conjectured that the earth of his native soil might also contain the same salt; and he was confirmed in that opinion by its astringent taste. At this time he held an important office in the Apostolic Chamber; and this discovery, which seemed to promise the greatest advantages, was considered as a real victory gained over the Turks, from whom the Italians had hitherto been obliged to purchase all their alum. Pope Pius II., who was too good a financier to neglect such a beneficial discovery, caused experiments to be first made at Viterbo, by some Genoese who had formerly been employed in the alum-works in the Levant, and the success of them was equal to his expectations. The alum, which was afterwards manufactured in large quantities, was sold to the Venetians, the Florentines, and the Genoese. The Pope himself has left us a very minute history of this discovery, and of the circumstances which gave rise to it[524]. Some pretend that Castro was several years a slave to a Turk who traded in alum[525]; others affirm that he had even been obliged to labour as a slave in alum-works[526]; and others, that he learned the art of boiling alum from a citizen of Corneto, a town in the dominions of the Pope, and from a Genoese, both of whom had acquired their knowledge in the Levant[527]. But as I do not wish to ascribe a falsehood to the Pontiff, I am of opinion that the history of this discovery must have been best known to him. He has not, indeed, established the year with sufficient correctness; but we may conclude from his relation that it must have been 1460 or 1465. The former is the year given by Felician Bussi; and the latter that given in the history of the city of Civita Vecchia.