178 Dr. Hulme's Experiments and Observations 



and at last was totally imperceptible. The phial was then takerr 

 out, and placed in water at about 62 ; by this change of 

 temperature, the frozen wood gradually thawed, and then re- 



gained its former lustre. 



The Light of Glow-worms. 



Exper. 4. A small phial, containing a luminous dead glow- 

 worm, was exposed to the cold of the frigorific mixture ; as 

 the coldness penetrated the phial, the light diminished, and at 

 length was totally extinct. But, by placing the phial in water 

 at about 6V, the glowing property of the insect soon returned. 

 In this experiment, the glow-worm was evidently congealed; 

 for it adhered to the side of the glass, and was covered with a 

 hoar-frost. This experiment was frequently repeated, and with 

 the same result. 



OBSERVATION. 



By these experiments we learn, that cold extinguishes spon- 

 taneous light in a temporary manner, but not durably, as the 

 substances of the third Section do; because the light revived 

 again in its full splendour, as soon as it was exposed to a mo- 

 derate degree of temperature. 



