4i 6 Dr. Hulme's Experiments and Observations 
OBSERVATION. 
From these experiments we learn, that hydrogen gas, in general, 
prevents the emission of spontaneous light, and also extinguishes 
it when emitted ; but, at the same time, it does not hinder its 
quick revival, when the subject of the experiment is again ex- 
posed to the action of atmospherical air; although the light 
may have been a considerable time in an extinguished state. 
§ v. 
The Effects of carbonic Acid Gas or fixed Air * on spontaneous 
Light. 
EXPERIMENTS. 
Exper. 1. At 10 P. M. a piece of fresh herring, weighing 
about three drams, was suspended in a wide-mouthed ten-ounce 
phial, filled With carbonic acid gas, and closed with a cork and 
bladder. It was retained there for three successive nights ; but 
emitted no light. 
Exper. e. The same experiment was made with a piece of 
herring, which was beginning to be luminous. On the next 
evening, the illumination was found to be extinct : nevertheless 
the herring was still kept in the gas, for three nights longer, 
but did not become lucid. 
Exper. 3. At 7 P. M. a piece of fresh mackerel was intro- 
duced above water, into a wide-mouthed bottle, holding 24 
ounces, which was completely filled with carbonic acid gas, 
* This gas was obtained from powdered chalk, or marble, and diluted sul- 
phuric acid. 
