i8o Dr. Hulme's Experiments and Observations 



cause on the next evening the light had somewhat revived; 

 which shows, that the heat of no° was not sufficient to ex- 

 tinguish totally all the light inherent in this piece of wood. 



Exper. 5. Finding that 110 degrees of heat did not 

 wholly extinguish the light of shining wood, a good many 

 fragments, of different sizes, were then submitted to the power 

 of boiling water, and detained therein for some time, in order 

 that the heat might penetrate them thoroughly. The effect was, 

 that the light became quickly extinct, and did not, as before, re- 

 appear on the following evening. 



The Light of Glow-worms. 



Exper. 6. A dead shining glow-worm was put upon two 

 ounces of water, contained in a wide-mouthed phial, at the tem- 

 perature of 58°. The phial was then sunk, about two or three 

 inches deep, in boiling-hot water; and, as the heat communicated 

 itself to the contents of the phial, the light of the glow-worm 

 became much more vivid. 



Exper. 7. Another lucid dead glow-worm was put into warm 

 water, at 1 14, , to see if that degree of heat would extinguish the 

 light ; but, on the contrary, its glowing property v/as aug- 

 mented. All the water was then poured off, yet the insect con- 

 tinued to shine for some length of time. 



Exper. 8. The effect of that heat which is obtained from dry 

 solid bodies by friction, was next tried upon the light of the 

 glow-worm. Two living glow-worms were put into a one- 

 ounce phial, with a glass stopple; and, though they were per- 

 fectly dark at the time, yet, if the phial was briskly rubbed with 

 a silken or linen handkerchief, till it became pretty warm, it 

 seldom failed to make them display their light very finely. 





