104* OBSERVATIONS ON SPONTANEOUS LIGHT-. 



§ 8. 



The FJfecls of a Vacuum on fpontaneous Light. 



EXPERIMENTS. 

 The light Is ex- £ x p. I. A piece of mining wood, of a moderate fize, was 



tmguifhed in _ . , Al . ~ ° . . , . 



vacuo, but beau- P ut under the receiver or an air-pump, in a darkroom; in 

 tifully reftored proportion as the air was extracted, the light was gradually 

 bv/dmiffionof extinguilhed, and at laft reduced to a mere point, juft vifible, 

 owing molt probably to a fmall refiduum of air, which is al- 

 ways left, even in the mofl perfect machine. Frefh air was 

 then leifurely admitted, and the light was immediately revived 

 in a very beautiful manner. This experiment was frequently 

 repeated, and always with the like effect. 



Exp. 2. Some luminous matter of a herring, uncommonly 

 bright, was fmeared upon a piece of red blotting paper, and 

 then fubmitted to the operation of the air-pump. The light 

 became fainter and fainter, as the inclofed air was withdrawn, 

 and at laft nearly vanifhed ; but brightened up as before, on 

 the influx of frefh air. The experiment was repeated, and 

 with the fame refult. 



SECTION XII, 



Experiments and Obfervations on folar Light, when imbibed by 

 Canton's Phofphorus. 



§ i. 



Tlw Effects of Heat on imbibed folar Light. 



J. The imbibed Light is rendered more vivid by a moderate 

 Degree of Heat. 



EXPERIMENTS. 



Canton's phof- E*P* 1 • Having prepared fome Canton's phofphorus, and 

 phorus fhines expofed it to the light of the fun, it was carried into the dark 

 Sated! 1 *" laboratory, to feparate the illuminated parts from thofe that 

 remained dark. In doing which, fofne luminous fragments 

 were placed upon the palm of the hand, and retained there 

 for fome time, when it was obferved, that the warmth, of the 

 hand confiderably increafed the degree of light. 



Exp. 2.. 



