Mr. Macartney’s Observations 
284 
from the beforementioned glow-worm, and from others killed 
in different ways, but it afforded no light. 
Experiment 3. — The sacs containing the luminous matter 
were cut from the bellies of living glow-worms, and shone 
uninterruptedly for several hours in the atmosphere, and after 
their light became extinct, it was revived by being moistened 
with water ; some of these were put into wa er in the first 
instance, in which they continued to shine unremittingly for 
48 hours. 
Experiment 4. — The luminous substance of a glow-worm 
was exposed to a degree of heat which would have been 
sufficient to inflame phosphorus, without increasing the bril- 
liancy of its light ; and farther, it could not be made to burn 
by being applied to a red hot iron, or to the flame of a candle. 
Experiment 5. — A delicate thermometer was introduced 
amongst some living glow-worms, during the time they gave 
out much light : the temperature of the room being 6 g, the 
instrument rose to 75, 7 6, and 77, according to circumstances, 
as the warmth was reflected from the hand, or dissipated by 
the worm crawling over cold substances. The luminous por- 
tion of the tail, when very brilliant, appeared to raise the 
thermometer more quickly than the other parts of the body, 
but it was not invariably the case. When shining strongly, I 
thought that the luminous rings communicated the sensation 
of warmth to the hand, but this was probably a deception, as 
the actual degree of heat was not sufficient for such an effect. 
It should however be mentioned, that in Templar’s observa- 
tions on the glow-worm, he said his feelings deceived him, if he 
did not experience some heat from the shining of the insect.* 
* Phil. Trans. No. 72. 
