In his 'History of Inventions, Discoveries,' &c. (Bohn's Standard Library), Beckmann, who, in treating of Alum, quotes several accounts of the works at Tolfa, says:—'The Pope himself has left us a very minute history of this discovery, and of the circumstances which gave rise to it;' and, alluding to the conflicting statements respecting the discoverer, he adds:—'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.[539] The former is the year given by Felician Bussi; and the latter that given in the History of the City of Civita Vecchia.' Beckmann's rendering of the Pope's history, though the account is here and there open to criticism, throws much light on the passage in the Indulgence and is otherwise very interesting. It is in these terms:—'A little before that period came to Rome John di Castro, with whom the Pontiff had been acquainted when he carried on trade at Basle, and was banker to Pope Eugenius. His father, Paul, was a celebrated lawyer of his time, who sat many years in the chair of Padua, and filled all Italy with his decisions; for lawsuits were frequently referred to him, and judges paid great respect to his authority, as he was a man of integrity and sound learning. At his death he left considerable riches, and two sons arrived to the age of manhood, the elder of whom, following the profession of the father, acquired a very extensive knowledge of law. The other, who was a man of genius, and who applied more to study, made himself acquainted with grammar and history; but, being fond of travelling, he resided some time at Constantinople, and acquired much wealth by dyeing cloth made in Italy, which was transported thither and committed to his care, on account of the abundance of alum in that neighborhood. Having by these means an opportunity of seeing daily the manner in which alum was made, and from what stones or earth it was extracted, he soon learned the art. When, by the will of God, that city was taken and plundered about the year 1453, by Mahomet II., Emperor of the Turks, he lost his whole property; but, happy to have escaped the fire and sword of these cruel people, he returned to Italy, after the assumption of Pius II., to whom he was related, and from whom he obtained, as an indemnification for his losses, the office of Commissary-General over all the revenues of the Apostolic Chamber, both within and without the city. While in this situation he was traversing all the hills and mountains, searching the bowels of the earth, leaving no stone or clod unexplored, he at length found some alum-stone in the neighborhood of Tolfa. Old Tolfa is a town belonging to two brothers, subjects of the Church of Rome, and situated at a small distance from Civita Vecchia. Here there are high mountains, retiring inland from the sea, which abound with wood and water. While Castro was examining these, he observed that the grass had a new appearance. Being struck with wonder, and inquiring into the cause, he found that the mountains of Asia, which enrich the Turkish treasury by their alum, were covered with grass of the like kind. Perceiving several white stones, which seemed to be minerals, he bit some of them, and found that they had a saltish taste. This induced him to make some experiments by calcining them, and he at length obtained alum. He repaired therefore to the Pontiff, and addressing him said, "I announce to you a victory over the Turk. He draws yearly from the Christians above three hundred thousand pieces of gold, paid to him for the alum with which we dye wool different colors, because none is found here but a little at the island of Hiscla, formerly called Aenaria, near Puteoli, and in the cave of Vulcan at Lipari, which, being formerly exhausted by the Romans, is now almost destitute of that substance. I have, however, found seven hills so abundant in it, that they would be almost sufficient to supply seven worlds. If you will send for workmen, and cause furnaces to be constructed, and the stones to be calcined, you may furnish alum to all Europe; and that gain which the Turk used to acquire by this article being thrown into your hands will be to him a double loss. Wood and water are both plenty, and you have in the neighborhood the port of Civita Vecchia, where vessels bound to the West may be loaded. You can now make war against the Turk: this mineral will supply you with the sinews of war, that is money, and at the same time deprive the Turk of them." These words of Castro appeared to the Pontiff the ravings of a madman: he considered them as mere dreams, like the predictions of astrologers; and all the cardinals were of the same opinion. Castro, however, though his proposals were often rejected, did not abandon his project, but applied to his Holiness by various persons, in order that experiments might be made in his presence on the stones which he had discovered. The Pontiff employed skilful people, who proved that they really contained alum; but lest some deception might have been practised, others were sent to the place where they had been found, who met with abundance of the like kind. Artists who had been employed in the Turkish mines in Asia were brought from Genoa; and these, having closely examined the nature of the place, declared it to be similar to that of the Asiatic mountains which produce alum; and, shedding tears for joy, they kneeled down three times, worshipping God, and praising his kindness in conferring so valuable a gift on our age. The stones were calcined, and produced alum more beautiful than that of Asia, and superior in quality. Some of it was sent to Venice and to Florence, and, being tried, was found to answer beyond expectation. The Genoese first purchased a quantity of it, to the amount of 20,000 pieces of gold; and Cosmo of Medici for this article laid out afterwards seventy-five thousand. On account of this service, Pius thought Castro worthy of the highest honors and of a statue, which was erected to him in his own country, with this inscription:—"To John di Castro, the Inventor of Alum;" and he received besides a certain share of the profit. Immunities and a share also of the gain were granted to the two brothers, lords of Tolfa, in whose land the aluminous mineral had been found. This accession of wealth to the Church of Rome was made, by the divine blessing, under the Pontificate of Pius II.: and if it escape, as it ought, the hands of tyrants, and be prudently managed, it may increase and afford no small assistance to the Roman Pontiffs in supporting the burdens of the Christian religion—Pii Secundi Comment . rer . memorab . quæ temp . suis contigerunt. Francof. 1614, fol. p. 185'
Dr. Georg Voigt, in his 'Enea Silvio de Piccolomini als Papst Pius der Zweite und sein Zeitalter,' vol. iii. pp. 546-48, says:—
'Ein Glückszufall brachte dem Papste noch eine ganz unerwartete Quelle von Einnahmen. Unter ihm wurden die berühmten Alaungruben von Tolfa entdeckt. Der genannte Giovanni de Castro, ein Mann der rührigsten Industrie, der zu Konstantinopel die Färbung italienischer Zeuge betrieben, bei der Eroberung der Stadt jedoch nichts als sein Leben und seine technischen Kenntnisse davongetragen, war der Finder. Umherschweifend auf dem einsamen culturlosen Waldgebirge, das sich unweit Civita-vecchia mit seinen Ausläufern bis zum Meer erstreckt, stöbernd unter den Steinen, Erden und Pflanzen mit dem eigenthümlichen Antriebe solcher Naturen, bemerkte er zunächst ein Kraut, das er auf den alaunhaltigen Bergen Asiens gesehen, dann weisse Steine, die der salzige Geschmack und gar die Auskochung als Alaun erwies. Freudig eilte er zum Papste und verkündete ihm den Sieg über die Türken, zunächst den Industriellen, da der Orient durch den Alaun jährlich über 300,000 Ducaten von den Christen verdiene. Von anderer Seite wird der Astrolog Domenico di Zaccaria aus Padua wenigstens als Mitentdecker angegeben.[540] Pius indess erwähnt nur de Castro. Er und die Cardinäle hielten die Entdeckung anfangs für eine alchymistische Träumerei. Doch bestätigten Sachverständige, dass das Gestein wirklich Alaun und dass es in jenen Bergen in betriebsfähiger Masse vorhanden sei; das reichliche Wasser der Gegend und der nahe Seehafen begünstigten den Bau. Es wurden Gewerbsleute aus Genua berufen, die einst bei den Türken den asiatischen Alaun behandelt; sie weinten vor Freude, als sie das Mineral erkannten, nach der Abkochung zeigte sich seine Güte: 80 Pfund hatten den Werth von 100 Pfund türkischen Alauns. Proben wurden nach Venedig und Florenz versandt. Genuesische Kaufleute schlossen zuerst einen Ankauf für 20,000 Ducaten ab. Dann Cosimo de' Medici einen für 75,000. Der Papst fasste den Vorsatz, das Geschenk Gottes auch zur Ehre Gottes, zum Türkenkriege zu verwenden; er ermahnte alle Christen, fortan nur von ihm, nicht von den Ungläubigen den Alaun einzukaufen, zumal da der seinige nach der Erfahrung besser und billiger sei.[541] Schon im Jahre 1463 wurde tüchtig in den Gruben von Tolfa gearbeitet, 8,000 Menschen waren dabei beschäftigt: der Finder wie die Besitzer des vorher unfruchtbaren Districtes erhielten eine Quote des Gewinnes, der dem apostolischen Schatze jährlich gegen 100,000 Ducaten einbrachte. In der Wahlcapitulation von 1464 wurden sämmtliche Einkünfte von Alaun für den Türkenkrieg bestimmt.'[542]
From Dr. Voigt's statements that as early as the year 1463, 8,000 men were employed in the alum-works of Tolfa, and that the profit to the apostolic treasury, after the claims of the discoverer and the proprietors had been duly recognized, amounted to 100,000 ducats a year, and from the date of the Pope's Brief quoted above, it would seem that the discovery could scarcely have been made later than 1462, the year assigned to it by Niccolo della Tuccia.
The following extract from R. Harrison's translation of A. von Reumont's 'Lorenzo de' Medici,' carries on somewhat further the history of this famous mine and of its position in regard to the Papal Government:—
'The Pope's affection and confidence were shown in various ways. The Roman depository, i.e., the Receiver's office, was handed over to the Medici, with the permission to choose as their representative Giovanni Tornabuoni, director of the Roman bank. New privileges were also granted to them in connection with their share in the farming of the alum-works of Tolfa. It was an important concession. In the days of Pope Pius II., Giovanni di Castro, son of the famous jurisconsult, Paolo, the principal co-operator in the revision of the Florentine statutes (finished in 1415), discovered alum-deposits in the rock while making geological investigations in the hilly country between Civita Vecchia and the territory of Viterbo, in the vicinity of Tolfa. He instantly perceived the importance of his discovery, which promised to free the West, hitherto poor in this mineral, from a tribute to the distant East, made more inaccessible by the Turkish conquests. In fact the produce soon amounted to 160,000 gold florins; and it is well known what sanguine hopes Pius II., whose eyes were directed towards the East, indulged, that this new source of revenue would aid his enterprises. Genoese houses had employed themselves with the alum-trade till the Medici concluded a contract with the Papal exchequer, which afterwards gave rise to many unpleasant misunderstandings with the financial department.'—(Vol. I. p. 275).
An account of the alum of Tolfa is also given in vol. v. chap. i., of the 'Voyages du P. Labat de l'Ordre des FF. Prescheurs, en Espagne et en Italie;' and in the article 'Alaun,' in the 'Oeconomische Encyclopädie,' by Dr. J. G. Krünitz, which is in part derived from Labat's work.