172 NATURE OF INSECT LIGHTS. 



Now for a word or two, borrowed, of course, from the 

 scientific page, but considerably at variance, respecting the 

 supposed nature and quality of this and other insect fires. 

 One experimentalist,"* having found that the glowworm's 

 light is neither diminished by immersion in water, nor increased 

 by application of heat, that it is not capable of ignition by 

 the flame of a candle, nor possessed of any sensible heat when 

 separate from the bearer's body, denies in this luminous mat- 

 ter the existence of any ordinary composition of phosphorus ; 

 suggesting, however, that the above facts are favourable to 

 the supposition of light being a quality of matter, rather than 

 a substance. 



Another examiner, t on the contrary, seems to have ascer- 

 tained that the glowworm's light-dilfusing substance is chiefly 

 albumen, combined with a portion of phosphorus ; and as 

 phosphorus can only become luminous by contact with oxygen 

 (supposing it uncombined with a fatty matter or albumen), he 

 considers this requisite supplied by means of the male insect's 

 respiration, which is strongest during flight ; while, in the 

 female, which flies not at all, the greater quantity of albumi- 

 nous substance contained in her thick body more than com- 

 pensates for the lesser respiratory action. 



Enough, at all events, has been ascertained about the illu- 

 minating matter of the glowworm's lamp to prove it perfectly 



Mr. Macartney, quoted by Kirby ami Speiice. 

 1 Mr. Macairc, quoted ill ' Naturalist's Library." 



