570 BOOK XII. 



the bottom of the caldron. The caldron, being thus prepared, is entirely 

 filled through a launder with water, and this is boiled with a fierce fire 

 until it bubbles. Then little by little eight wheelbarrow loads of the 

 material, composed of roasted rock moistened with water, are gradually 

 emptied into the caldron by four workmen, who, with their shovels which 

 reach to the bottom, keep the material stirred and mixed with water, and 

 by the same means they lift the lumps of undissolved rock out of the 

 caldron. In this manner the material is thrown in, in three or four lots, at 

 intervals of two or three hours more or less ; during these intervals, the 

 water, which has been cooled by the rock and material, again begins to boil. 

 The water, when sufficiently purified and ready to congeal, is ladled out and 

 run off with launders into thirty troughs. These troughs are made of oak, 

 holm oak, or Turkey oak ; their interior is six feet long, five feet deep, and 

 four feet wide. In these the water congeals and condenses into alum, in the 

 spring in the space of four days, and in summer in six days. Afterward the 

 holes at the bottom of the oak troughs being opened, the water which has 

 not congealed is drawn off into buckets and poured back into the caldron ; 

 or it may be preserved in emptj^ troughs, so that the master of the workmen, 

 having seen it, may order his helpers to pour it into the caldron, for the water 

 which is not altogether wanting in alum, is considered better than that which 

 has none at all. Then the alum is hewn out with a knife or a chisel. It is 

 thick and excellent according to the strength of the rock, either white or 

 pink according to the colour of the rock. The earthy powder, which remains 

 three to four digits thick as the residue of the alum at the bottom of the 

 trough is again thrown into the caldron and boiled with fresh aluminous 

 material. Lastly, the alum cut out is washed, and dried, and sold. 



Alum is also made from crude pyrites and other aluminous mixtures. 

 It is first roasted in an enclosed area ; then, after being exposed for some 



eventuated until the appearance of one John de Castro. From the Commentaries of 

 Pope Pius II. (1614, p. 185), it appears that this Italian had been engaged in 

 dyeing cloth in Constantinople, and thus became aware of the methods of making 

 alum. Driven out of that city through its capture by the Turks, he returned to Italy and 

 obtained an office under the Apostolic Chamber. While in this occupation he discovered a 

 rock at Tolfa which appeared to him identical with that used at Constantinople in alum 

 manufacture. After experimental work, he sought the aid of the Pope, which he obtained 

 after much vicissitude. Experts were sent, who after examination "shed tears of joy, they 

 kneeling down three times, worshipped God and praised His kindness in conferring such a gift 

 on their age." Castro was rewarded, and the great papal monopoly was gradually built upon 

 this discovery. The industry firmly established at Tolfa exists to the present day, and is the 

 source of the Roman alum of commerce. The Pope maintained this monopoly strenuously, 

 by fair means and by excommunication, gradually advancing the price until the consumers had 

 greater complaint than against the Turks. The history of the disputes arising over the 

 papal alum monopoly would alone fill a volume. 



By the middle of the 15th Century alum was being made in Spain, Holland, and 

 Germany, and later in England. In her efforts to encourage home industries and escape the 

 tribute to the Pope, Elizabeth (see Note on p. 283) invited over " certain foreign chymistes and 

 mineral masters " and gave them special grants to induce them to " settle in these 

 realmes." Among them was Cornelius Devoz, to whom was granted the privilege of " mining 

 and digging in our Realm of England for allom and copperas." What Devoz accomplished 

 is not recorded, but the first alum manufacture on a considerable scale seems to have been in 

 Yorkshire, by one Thomas Chaloner (about 1608), who was supposed to have seduced 

 workmen from the Pope's alum works at Tolfa, for which he was duly cursed with all the 

 weight of the Pope and Church. (Pennant, Tour of Scotland, 1786). 



