HISTORICAL NOTES. 175 



act, by which these insects separated light from 

 their food, and afterwards secreted it in a sensible 

 form. When we recall the chemical theories in 

 vogue at that period, we find that BrugnatelliV 

 opinion is not so ridiculous as one would be apt 

 to suppose. 



Carradori, another Italian naturalist, appears 

 to have admitted Brugnatelli's opinion ; but know- 

 ing that the Lampyridce could extinguish or emit 

 their light at will, he thought that they effected 

 this with a peculiar membrane acting as a screen, 

 by which the insect (Lampyris italica) hid its 

 light. The existence of this membrane was after- 

 wards denied by Macartney in the ' Philosophical 

 Transactions for 18 10/ But Carradori caused 

 science to take a step forward when he proved 

 that the light of Lampyris italica was not imme- 

 diately extinguished in vacuo, in oil, or under 

 water, as the light of a candle, or that of common 

 phosphorus would be. 



Boyle, Hume, and Macaire have all observed 

 that the phosphorescence of certain dead organic 

 matters was extinguished, at least partially, in 

 vacuo. Boyle's experiments on this subject were 

 published in the ' Philosophical Transactions' for 

 1668. Although he certainly did happen once to 

 extinguish the light of phosphorescent wood, in 

 vacuo, completely, he never succeeded in totally 

 extinguishing that emitted by dead fish. 



