454 TH ^ INTELLECTUAL RISE IN ELECTRICITY. 



But the years went by, and if the discoveries were made 

 nobody mentioned them, and the strange light which 

 Picard had seen in the barometer was as little remembered 

 as the glow which Guericke had obtained years before 

 from his sulphur ball. 



There had been known, since the beginning of the 

 century, a mineral, sometimes termed the Bologna stone, 

 sometimes the Bononian stone, from the place of its dis- 

 covery, which would become luminous in the dark. 1 It had 

 been accidentally found by one Casciorolus, a shoemaker 

 who had deserted his trade for alchemy, and who gave it 

 the name of "lapis Solaris," because, from its illuminating 

 properties, he conceived it especially suitable for the trans- 

 mutation of silver into gold the alchemical sol. As the 

 Italian chemists seem to have agreed in this opinion, the 

 stone soon became in great demand and brought fabulous 

 prices, which were maintained despite the claim of Potier, 

 a French chemist, that he could produce it artificially. In 

 1666, the English Royal Society records the death of a 

 clergyman who was said to have exclusively possessed the 

 art, without communicating it to any one. 



The value placed upon the substance which was 

 barium sulphide, frequently used now as a basis for the 

 so-called luminous paint incited the chemists to endeavor 

 to imitate it; with the result that, at about the time of 

 Picard's observation of the light in his barometer, Brand, 

 of Germany, produced a light-giving substance from 

 animal excretions, and sold the secret of its manufacture 

 to Krafft. Krafft named it "phosphorus" and took it to 

 England, where it was exhibited to the king, and, as we 

 nave already seen, it constituted one of the most interest- 

 ing of the Gresham College curiosities. In Germany, 

 Hunkel, who learned of it from Krafft, published, in 1678, 

 a pamphlet describing it, and the interest excited in Eng- 



^eckmann: A History of Inv'ns and Discoveries. 3d ed., 1817, vol. 

 iv., 419. Roscoe and Schorlemmer: A Treatise on Chemistry. N. Y., 

 1883, vol. i., 457. 



