128 PHILOSOPHICAL TRANSACTIONS. [aNNO 1792. 



were very mimerous; as he supposed that he saw at least 150 of them. Their 

 light did not much exceed that of Mons Porphyrites Hevelii. 



111. Experiments and Observations on the Production of Light from Different 

 Bodies, by Heat and by Attrition. By Mr. Thos. Wedgwood, p. 28. 



Pliny was well acquainted with the luminous appearance of rotten wood, and 

 of the eyes of dead fish. From this time nothing is found relative to the phos- 

 phorism of bodies, till the beginning of the l6th century, when Benvenuto 

 Cellini, in his Art of Jewellery, mentions his having seen a carbuncle shine in 

 the dark like coals nearly burnt out; and relates a story of a coloured carbuncle 

 having been found in a vineyard near Rome, by its shining in the night. About 

 the year 1639, Vincenzo Cascariolo, of Bologna, discovered, by accident, that 

 when a certain stone found in that neighbourhood was calcined in a particular 

 manner, it acquired the remarkable property of absorbing the light of the sun, 

 of retaining it for some time, and of emitting it in the dark: subsequent ex- 

 perimenters found it to do the same with the light of a candle. In 1663, Mr. 

 Boyle observed a particular diamond to give out a light almost equal to that of a 

 glow-worm, when heated, rubbed, or pressed; and investigated very fully the 

 nature of the light of dead fish, flesh meat, and rotten wood. In ]677, Bald- 

 win of Misnia discovered, in the residuum of a distillation of chalk and nitrous 

 acid, a phosphorus similar in its properties to the Bolognian, but not possessing 

 the phosphoric virtue in so eminent a degree. In 1705, Mr. Francis Haukesbee 

 found that glass rubbed on glass, in common air, in the vacuum of an air-pump, 

 or under water, "exhibited a considerable light." In 1/24, M. du Fay dis- 

 covered that almost all substances which could be reduced to a calx by fire only, 

 or after solution in the nitrous acid, absorbed and emitted light like the phos- 

 phorus of Cascariolo and of Baldwin; and that some diamonds, emeralds, and 

 many other precious stones emitted light in the dark, after being exposed to the 

 rays of the sun. About the same time, Beccaria of Turin (bund almost every 

 body in nature to be luminous after a similar exposure: he added also this very 

 important discovery; that an artificial phosphorus, exposed to the light in a 

 coloured glass phial, emits in the dark rays of the identical colour of the 

 phial. Mr. Margraaf, by an analysis of the Bolognian stone, shows that it con- 

 tains vitriolic acid united to calcareous earth, and that all gypseous stones treated 

 like the Bolognian, provided they are pure from iron, become phosphorescent. 

 About the year 17^)4, Mr. Canton made a phosphorus of sulphur and oyster 

 shells calcined together, and distinguished himself by many curious experiments 

 made with it; he found that his phosphorus might be made to shine by heating 

 it, after it had ceased to be luminous of itself, but that the same heat would 

 have this effect for a certain time only. Heat has been observed by several of 



