BASIS OF ANIMAL PHOSPHORESCENCE. 109 



of the light itself, but a new indirect expenditure in the produc- 

 tion of invisible calorific rays. Our eyes recognize heat mainly 

 as it is conveyed in certain rapid ethereal vibrations associated 

 with high temperatures without passing through the interme- 

 diate low ones ; so that if the vocal production of a short atmos- 

 pheric vibration were subject to analogous conditions, a high 

 note could never be produced until we had passed through the 

 whole gamut, from the discontinuous sounds below the lowest 

 bass, up successively through every lower note of the scale till 

 the desired alto was reached. 



"There are certain phenomena long investigated, yet little 

 understood, and grouped under the general name of ' phospho- 

 rescent,' which form an apparent exception to this rule, espe- 

 cially where nature employs them in the living organism, for it 

 seems very difficult to believe that the light of a fire-fly, for 

 instance, is accompanied by a temperature of 2000° or more 

 Fahr., which is what we should have to produce to gain it by 

 our usual processes. That it is, however, not necessarily impos- 

 sible, we may infer from the fact that we can by a known physi- 

 cal process produce a still more brilliant light without sensible 

 heat, where we are yet sure that the temperature exceeds this. 

 No sensible heat accompanies the fire-fly's light any more than 

 need accompany that of the Geissler tube ; but this might be 

 the case in either instance, even though heat were there, owing 

 to its minute quantity, which seems to defy direct investigation. 

 It is usually rt:i-j-?/w^^ with apparent reason, that the insect's light 

 is produced without the invisible heat that accompanies our 

 ordinary processes, and this view is strengthened by study of 

 the fire-fly's spectrum, which has been frequently observed to 

 diminish more rapidly toward the red than that of ordinary 

 flames. Nevertheless this, though a highly probable and rea- 

 sonable assumption, remains assumption rather than proof, until 

 we can measure with a sufficiently delicate apparatus, the heat 

 which accompanies the light, and learn not only its quantity, 

 but what is more important, its quality" (pp. 98, 99). 



Under " Photometric Observations," the authors continue : 

 " The first impression in viewing the light of the Pyrophorus 

 noctiliicus through a spectroscope is that it consists essentially 



