Mr . Macartney's Observations 
gB 6 
sufficient to allow the animal to preserve its figure ; being' 
insulated, it was electrified, and sparks drawn from it, which 
had not the slightest effect ; the experiment was repeated 
several times with different individuals, but without exciting 
the anirhals to throw out light. 
Experiment 11.— - Some hemispherical medusae were placed 
in contact with the two ends of an interrupted chain, and 
slight electric shocks passed through them. During the very 
moment of their receiving the shock no light was visible, but 
immediately afterwards the medusae shone like illuminated 
*/ 
wheels, which appearance remained for some seconds. Upon 
the closest inspection with a magnifying glass, no contractile 
motion could be perceived to accompany the exhibition of the 
light. The application of electricity in this instance seems to 
have acted merely as a strong mechanic shock. 
The above experiments on the luminous medusae were 
made at Herne, with the assistance of George May, Esq. of 
Stroud-house, and in the presence of a large company, capa- 
ble of accurately distinguishing their results. 
It seems proved by the foregoing experiments, that so far 
from the luminous substance being of a phosphorescent nature, 
it sometimes shews the strongest and most constant light, 
when excluded from oxygene gas ; that it in no circumstances 
undergoes any process like combustion, but is actually in- 
capable of being inflamed ; that the increase of heat, during 
the shining of glow-worms, is an accompaniment, and not an 
effect of the phenomenon, and depends upon the excited state 
of the insect; and lastly, that heat and electricity increase the 
exhiti ion of light, merely by operating like other stimuli 
upon the vital properties of the animal. 
