646 ANNUAL REGISTER, 1810. 



Experiment 9 Some of the 



scintillating and hemispherical 

 species of medusae contained in a 

 small glass jar were introduced 

 into the receiver of an air-pump, 

 and the air being exhausted, they 

 shone as usual when shaken; if 

 any difference could be perceived, 

 the light was more easily excited, 

 and continued longer in vacuum. 



I wished next to try the influ- 

 ence of electricity on the luminous 

 property of animals. 



Experiment 10. — A medusa he- 

 mispherica was placed in a small 

 glass dish, containing a quantity 

 of water merely sufficient to allow 

 the animal to preserve its figure ; 

 being insulated, it was electrified, 

 and sparks drawn from it, which 

 liad not the slightest effect ; the 

 experiment was repeated several 

 times with different individuals, 

 but without exciting the animals 

 to throw out light. 



Experiment 11.— .Some hemi- 

 spherical medusae were placed in 

 contact with the two ends of an 

 interrupted chain, and slight elec- 

 tric shocks passed through them. 

 During the very moment of their 

 receiving the shock no light was 

 visible, but immediately afterwards 

 the medusiE shone like illuminated 

 wheels, which appearance re- 

 mained for some seconds. Upon 

 closest inspection with a magnify- 

 ing 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 

 Heme, witli the assistance of Geo. 

 May, esq. of Stroud-house, and 



in the presence of a large com- 

 pany, capable of actually distin- 

 guishing their results. 



It seems proved by the forego- 

 ing experiments, that so far from 

 the luminous substance being of a 

 phosphorescent nature, it some- 

 times shews the strongest and 

 most constant light, when exclud- 

 ed from oxygen gas ; that it in 

 no circumstances undergoes any 

 process like combustion, but is 

 actually incapable of being in- 

 flamed : that the increase of heat, 

 during the shining of glow-worms, 

 is an accompaniment, and not an 

 effect of the phaenomenon, and 

 depends upon the excited state of 

 the insect ; and lastly, that heat 

 and electricity increase the exhi- 

 bition of light, merely by ope- 

 rating like other stimuli upon the 

 vital properties of the animal. 



In confirmation of these opi- 

 nions, I may quote the high au- 

 thority of the secretary of this 

 society, who has found that the 

 light of the glow-worm is not 

 rendered more brilliant in oxygen, 

 or in oxygenated muriatic gas, 

 than in common air ; and that it 

 is not sensibly diminished in hy- 

 drogen gas. 



I may farther add, that Spal- 

 lanzani's experiments of diffusing 

 the luminous liquor of the me- 

 dusa in water, milk, and other 

 fluids, are in direct contradiction 

 of his own theory, as is also the 

 extinction of the light of these 

 mixtures by the application of a 

 high degree of heat. 



If the light emitted by animals 

 were derived from their food, or 

 the air they respire, as supposed 

 by Carradori, the phaenomenon 

 should be increased or diminish- 

 ed, according to the quantity of 



