6 THE CHEAPEST FORM OP LIGHT. 



light veiy finel^^ This experiment was very frequently repeated. It 

 had the same illuminating effect upon the light of a dead glow-worm. 



Exper. 9. The complete influence of 212 degrees of heat was now 

 applied to the light of a glow-worm, by pouring upon one when dead, 

 but in a luminous state, some boiling water. Its light was instantly ex- 

 tinguished thereby and did not revive. The experiment was repeated 

 and with the same result. 



Macaire^^ (quoted by Becquerel) found that tlie luminous matter taken 

 from the body of a glow-worm and heated, increased in brilliancy up to 

 a temperature of about 41° C, after which the light diminished, became 

 reddish, and ceased at 52° C. An electric current increased the lumi- 

 nosity in both the living insect and in the luminous part separated from 

 the remainder of the body, but ceased to have any effect in a vacuum. 

 Oxygen and carbon monoxide increased the light of the living insect and 

 of the luminous matter tal^en from its body, but the light ceased in a 

 vacuum, in hydrogen, in carbon dioxide, in suli)hurous anhydride, and 

 in sulphureted hydrogen. 



Carus\ observed that the luminous matter taken from the body of the 

 glow-worm ceases to shine when dried, but glows again when moistened- 



MaiteucciX found that the phosphorescent substance of the Italian 

 glow-worm (Lmnpyris Italica) soon ceased to glow in hydrogen or in 

 carbon dioxide, but shone decidedly brighter in oxygen than in air, the 

 oxygen being consumed and carbon dioxide appearing. He drew the 

 conclusion that the production of light in this insect is entirely due to 

 the combination of ox3''gen with carbon, which is one of the elements 

 of the phosphorescent matter. The greatest brilliancy occurred at a tem- 

 perature of 37° or 38° Cent., but all phosphorescence ceased above 50° 

 or below — 6° Cent. 



Robert § found that a glow-worm cut in halves continued to glow for 

 half an hour, when the light ceased, but commenced again on the near 

 approach of a candle, and continued as bright as ever for thirty-six 

 hours, after which it was impossible to renew it. 



Pastetir || has examined the specti'a of our Pyrophorus without finding 

 any appearance of bright or dark lines. He states that M. Gernez has 

 made a similar observation on the spectrum of the glow-worm. 



Becquerel^ gives a good summary of the results of ])revious observers. 

 Since phosphorescent solids give banded spectra and thus differ from 

 ignited solids and liquids which have continuous spectra, M. Becquerel 



* " Bibliotheque Univ. de Geneve," 1821. 



t "Analecten zer Natur- und Heilkunde," Leipzig, 1829 ; see also Comtes Reiidus, 

 lix, p. 607, 1864. 

 X "Ann. de chim. et de phys.," Ill, ix, p. 71, 1843 ; also in C. R., xvii, p. 309. 

 ?C. R., xvii, p. 627, 1843. 

 11 C. R., lix, p. 509, 1864. 

 i"Lalumiere," 1867. 



