22 EYE SPY 



with animal life, which, though dwelling in depths 

 scarce reached by the faintest gleam from the sun, 

 swim about enveloped in their self-illumined halo. 



While all these phenomena come under the 

 general term of phosphorescence, the inference of 

 the presence of phosphorus is incorrect ; many 

 substances without a trace of phosphorus in their 

 constitution emit light with equal brilliancy. 



The well-known commercial article called " lu- 

 minous paint " is an apt example, which, while 

 containing no trace of phosphorus, glows like fox- 

 fire at night, especially after having been exposed 

 to the sun's rays during the day, giving forth in 

 the dark hours the light which it has thus ab- 

 sorbed, and being thus of utility in its application 

 to clock faces and match-boxes. 



Calcined lime and burnt oyster-shells, in com- 

 bination with certain acids, become luminous at 

 «;«u<- u,, 4.U,. ^;^^;i — „^, „r „T i_' _i 



