wild, that there must be minerals in the neighbourhood, and after making some search at length discovered alum. As there was, however, no one who understood the method of preparing it, he privately engaged workmen belonging to the pope's alum works, and it is said, that as soon as the pontiff heard of this, he endeavoured to recal them by threats and anathemas. This however had no effect, and the work soon succeeded so well, that more of the same kind were soon established. Here too, however, the spirit of monopoly, again broke out, and king James, after appropriating the work to himself prohibited the importation of foreign alum.*

The most ancient alum work in Sweden was established at Andrarus in Scania, in 1637. The number gradually increased, and in 1767, when Bergman published his dissertation, there were seven.f

The above sketch contains all the information I have been enabled to obtain concerning the commencement of this art in various European countries. It is not necessary, to continue the enumeration to a later period, as works have become very numerous, and flourish or decay, according to the facility of obtaining the proper mineral, and the expence attending the manufacture of it.

One observation may be made at the conclusion of

*To prevent the too frequent repe'ition of references, I mention here, that most of the above facts are obtained from Beckmann.

↑ Bergman's Chemical Essays, vol. 1. p. 341.

There is an account of the alum works in England, in 1678, contained in the Philosophical Transactions. See the abridgment by Drs. Hutton, Shaw and Pearson, v. 2. p. 459.

this section.

Indeed it seems to flow from a review

of the narrative now given. This art was no sooner introduced in succession into various countries of Europe, than the respective sovereigns who engrossed its manufacture, endeavored to monopolize the advantages to be derived from it. The anathemas of the church, and the threats of corporal penalties were hurled on those who presumed to investigate the processeses of the art, or to improve the bounties of nature. How vain have these efforts proved, and how futile must be the effects of similar monopolies at the present day, if science and ingenuity are only directed to a discovery of the secret.

2. NOTICE OF THE SUBSTANCES FROM WHICH ALUM IS OBTAINED.

It will form a proper introduction to this part of our subject, to notice in a brief manner, the mineralogical history of this substance. The alum of commerce, is rarely, if ever, a natural production, but is manufactured from minerals that contain it, or is procured by chemical processes, which will hereafter be described. "It has even been doubted whe"ther alum is ever a natural production, since it is

enveloped in so singular a manner in the mineral "substances which contain it, or from which it is procured or produced. From several of these, "however, it is obtained merely by their exposure "to the operation of the atmosphere on them, and "in volcanic countries, it is largely met with, en"crusting lavas." It has hence certainly as much

right, as many other substances, to be considered a distinct mineral, and accordingly we find it so arranged in most systematic works. The following is the division by Jameson, of the salts of alumina, (the basis of alum.) Species 1, alum. Species 2, rock butter. The first is sometimes called plumose alum, and it generally occurs as an efflorescence in aluminous minerals.* Thus it is found in this state, on the surface of bituminous shale and slate clay, at Hurlet near Paisley in Scotland, also encrusting alum slate near Moffat in Dumfrieshire, and at Whitby in Yorkshire. On the continent of Europe, it is met with in many places, as in the alum slate rocks near Christiana in Norway, in coal mines in Bohemia, on bituminous schistus at Gott wig in Austria and on grey argillite in Carinthia.

As a volcanic production, it is found at the Solfatara, a few miles from Naples. This is a small plain at the top of a hill, covered with a white soil and exhaling sulphureous vapours, which during the night emit a pale blue lambent flame. The ground even at the surface is considerably warm, proceeding no doubt from subterraneous fire. The white clayey soil of this plain, being constantly penetrated by these vapours, and the exhalations during the night, being for the most part mixed with the dew, and thus returned upon the surfac, cause it to be covered with a slight saline efflorescence, and this

*Phillip's Mineralogy. Article Alum.

"Alum is rarely found massive, that which is met with in the island of Milo, most nearly approaches to this character. If taken away, it shortly appears again, whence it is supposed to be merely close aggregations of efflorescence." Phillips.

efflorescence is alum, ready formed, which requires only purification in order to fit it for use. Alum is also a volcanic product in the islands of Stromboli and Milo in the Mediterranean, and in several other parts of Italy. The second species, the rock or mountain butter, is hardly worth attention, except in a mineralogical point of view. It is composed of alum mixed with alumina and oxide of iron.

Having thus stated that the alum of commerce is obtained, first, from what is called by mineralogists native or plumose alum, we add, that a second species from which it is procured is alum stone. The colour of this substance is generally a greyish or yellowish white, and it occurs massive, and in veins running through argillaceous rocks at Tolfa (about which we have already spoken) near Civita Vecchia in the dominions of the church. Sometimes it is seen in nests and kidneys and is penetra. ted by veins of quartz. Alum stone is also found in various places in Upper Hungary. Here it oc curs in beds, and pyrites, native sulphur and quartz are often found dispersed through it. These are the only localities of this mineral, if we except the one mentioned in the note. It is from the alum stone of La Tolfa, that the Roman alum of commerce iş made.

A third mineral from which this substance is procured, is alum slate or aluminous schistus.There are two varieties of it. The common A. S, and the glossy or shining A. S. The lustre of the

+"A similar kind of ore has been discovered in rocks at Poliniere in Brittany." Rees' Cyclopedia. Art. Alum.

last is more of a metallic nature than that of the first. Both varieties are found in Norway, at Whitby in England and at Freyberg in Saxony. Esmark observed a vein of alum slate about two fathoms wide at Telkobanya in Hungary.* This mineral is also found in Saxony, Bohemia, Scotland, and some parts of France. It commonly occurs in the vicinity of coal, and it seems to differ in no respect from bituminous shale, impregnated with pyrites.† The alum of Great Britain and the north of Europe, is almost entirely made of it, for which use, the second variety is said to be the best adapted.

Alum earth is the fourth mineral used for the above This is of a blackish brown colour, has a purpose. strong resemblance to bituminized wood, and when left exposed to a moist atmosphere, becomes warm and occasionally takes fire. Hence, it has sometimes been used for fuel. Alum earth occurs frequently in beds of large magnitude in alluvial land, and sometimes also in the floetz trap formation. It is found in Bohemia, Saxony, Austria, Naples, Hungary, and in the Vivarrais in France-and in all these places is employed in the manufacture of alum,

The above minerals are those from which the alum of commerce is principally procured. Pyritous and pyrito bituminous matters are however often found to afford vitriolic salts, by the combined action of heat and moisture. Hence it is that the upper strata of the softer aluminous, schistus, of the alum earth, and the sulphurcous peats are often im

Jameson, Vol. 1. p. 433.

Rees' Cyclopedia.