6g 
Sir H. Davy's researches on flame. 
which the hydrogene is inflamed ; the hydrogene will be 
found to burn in whatever part of the bottle the tube is 
placed : after the hydrogene is extinguished, introduce lighted 
sulphur; this will burn for some time, and after its extinction, 
phosphorus will be as luminous as in the air, and, if heated 
in the bottle, will produce a pale yellow flame of considerable 
density. 
In cases when the heat required for chemical union is very 
small, as in the instance of hydrogene and chlorine, a mix- 
ture which prevents inflammation will not prevent combina- 
tion, i. e. the gases will combine without any flash. This I 
witnessed in mixing two volumes of carburetted hydrogene 
with one of chlorine and hydrogene ; muriatic acid was formed 
throughout the mixture, and heat produced, as was evident 
from the expansion when the spark passed, and the rapid 
contraction afterwards, but the heat was so quickly carried 
off by the quantity of carburetted hydrogene that no flash 
was visible. 
In the case of phosphorus, which is combustible at the 
lowest temperature of the atmosphere, no known admixture 
of elastic fluid prevents the luminous appearance; but this 
seems to depend upon the light being limited to the solid 
particles of phosphoric acid formed; whereas to produce flame, 
a certain mass of elastic fluid must be luminous ; and there is 
every reason to believe, that when phosphuretted hydrogene 
explodes in very rare air, it is only the phosphorus which is 
consumed. Any other substance that produces solid matter 
in combustion would probably be luminous in air as rare, or 
in mixtures as diluted, as phosphorus, provided the heat was 
elevated sufficiently for its combustion. I have found that 
