To render it capable of shining in the dark, a piece particularly heavy, foliaceous and pure, must be selected[1046]. After being made red-hot, it is pounded and reduced to a fine powder, which, by means of a solution of gum-tragacanth, is converted into a kind of paste, and formed into small cakes. When these are dried, they are brought to a state of ignition between coals, and then suffered to cool; after which they are preserved from the air and moisture in a close vessel. If one of these cakes be exposed a few minutes to the light, and then carried into a dark place, it will shine like a burning coal. It appears therefore to attract the light, or to be as it were a light-magnet. This power of emitting light becomes lost in the course of time; but it may be restored at first by heating, and afterwards by exposure again to ignition. I shall pass over the rules necessary to be observed in the numerous experiments made with this stone, as well as the consequences deduced from them. The former may be found in works on chemistry, and the latter in those on natural philosophy.
All the Italian writers who first describe this remarkable phænomenon give the following account of the discovery. At the beginning of the seventeenth century there was at Bologna a shoemaker, who, having quitted his trade, applied himself to chemical labours, and particularly to the art of gold-making. I do not know whether those who have made the very just remark, that many shoemakers go beyond their last into the province of other arts or sciences, have mentioned among the already numerous instances this shoemaker of Bologna, whose name was Vincentius Casciorolus; but he certainly deserves a niche in the temple of fame, because it may with truth be said of him, that he kindled up a light to the learned; whereas the shoemaker of Görlitz, Jacob Behmen, darkened or extinguished the existing light to the learned as well as the unlearned, so that the minds of many are still left in obscurity.
In the year 1602 Casciorolus came to Scipio Begatello of Bologna, who at that time was particularly well known by his attachment to the art of gold-making, and showed him this stone, under the mystical name of lapis solaris, which, on account of its weight and the sulphur it contained, as well as of its attracting the golden light of the sun, seemed to be fit for converting the more ignoble metals into gold, the sol of the alchemists. He showed it also to J. A. Maginus, the professor of mathematics; and the latter, who in all probability was no adept, sent both the natural and prepared stones to princes and learned men, and perhaps contributed more than any other person to make known this singular discovery[1047].
It however appears as if the Italian chemists concealed the preparation of this stone, or were not all acquainted with it. It was always said to be a secret known only to a few individuals in Bologna. Misson, who was there in the year 1690, asserts that Bartholomew Zanichelli was the only person at that time in possession of it. In 1666 it was announced in the Philosophical Transactions[1048], that a clergyman, who exclusively possessed the art, had died, without communicating it to any one. Niceron[1049], Lemery[1050], and many others say, that Homberg, during his residence at Bologna, had again discovered it, after many experiments; and that Lemery learned it from him and made it publicly known.
This however cannot be altogether true; for in the year 1622, P. Potier, or Poterius, a French chemist, who lived at Bologna, taught the preparation of it in his work already quoted, as did Kircher[1051] in 1641, and the jesuit Casati[1052] in 1686; though the process then employed was indeed not the best or most convenient; the proper method being first found out, after many accurate experiments, by the German chemist Marggraf, who showed also how similar light-magnets or luminous stones can be prepared from most of the heavy spars and fluor-spars[1053].
But even at present, those who prepare this stone for sale at Bologna talk in such a manner as if the secret were known to them alone. This was the case, in 1771, with the director of the institute in that city[1054]. Keysler purchased a piece, as large as a dried fig pressed flat, for about two or three paoli.
I shall embrace this opportunity of bringing to recollection, from De Thou’s history of his own times, a relation which indeed contains many things incredible, and in all probability exaggerated, yet seems to be too well confirmed to be altogether rejected as false. If this be admitted, it may then be conjectured that, about the year 1550, either the Bologna stone, or what at present is called phosphorus and pyrophorus, was known to a few individuals. In the above year, when Henry II. king of France made his solemn entrance into the town of Boulogne, on its restoration by the English, a stone from India, which was not hard, which had a luminous appearance like fire, and which could not be touched without danger, was presented to him by a stranger. For the truth of this account De Thou refers to the testimony of J. Pipin, in a letter to Ant. Mizaud, who asserts that he himself saw the stone. Morhof, who seems inclined to consider this stone as that of the philosophers[1055], remarks that this passage is found in the first Paris edition in octavo, and in the Frankfort re-impressions, both in folio and octavo; but not in the other editions. He quotes also the words from the letter to Mizaud, which must be printed somewhere, but in what work I do not know. It appears that the historian inserted it almost without any change.
[We may take this opportunity of describing one or two other pyrophori: thus Canton’s pyrophorus is prepared by heating a mixture of three parts of sifted calcined oyster-shells with one part of flowers of sulphur to an intense heat for one hour; Homberg’s, by mixing equal weights of alum and brown sugar, and stirring the mixture over the fire in an iron ladle until quite dry; it is then put into an earthenware or coated glass bottle and heated red-hot as long as a flame appears at the mouth; it is then removed, carefully stopped and suffered to cool. The black powder which it contains becomes glowing hot when exposed for a few minutes to the air.]
FOOTNOTES
[1042] [Several localities are now known for this peculiar variety of heavy spar; among others we may mention Amberg in the Upper Palatinate, and near Osterode in the Harz mountains.]