Sir H. Davyds researches on flame. 6 g 
being the same, and impermeable to all flames at common 
temperatures, the flames of the most combustible substances, 
and of those which produce most heat, will most readily pass 
through it when it is heated, and each will pass through it at 
a different degree of temperature. In short, all the circum- 
stances which apply to the effect of cooling mixtures upon 
flame, will apply to cooling perforated surfaces. Thus, the 
flame of phosphuretted hydrogene at common temperatures, 
will pass through a tissue sufficiently large not to be imme- 
diately choaked up by the phosphoric acid formed, and the 
phosphorus deposited.* A tissue of 100 apertures to the 
square inch, made of wire of will at common tempera- 
tures intercept the flame of a spirit lamp, but not that of 
hydrogene ; and when strongly heated, it will no longer 
arrest the flame of the spirit lamp. A tissue which will not 
interrupt the flame of hydrogene when red hot, will still in- 
tercept that of olefiant gas, and a heated tissue which would 
communicate explosion from a mixture of olefiant gas and 
air, will stop an explosion from a mixture of fire-damp, or 
oarburetted hydrogene. 
The ratio of the combustibility of the different gaseous 
matters are likewise to a certain extent as the masses of 
heated matter required to inflame them.-f* Thus an iron 
* If a tissue containing above 700 apertures to the square inch be held over the 
flame of phosphorus or phosphuretted hydrogene, it does not transmit the flame till 
it is sufficiently heated to enable the phosphorus to pass through it in vapour. Phos- 
phuretted hydrogene is decomposed in flame, and acts exactly like phosphorus. 
+ It appeared to me in these experiments, that the worst conducting and best 
radiating substances required to be heated higher for equal masses to produce the same 
effect upon the gases ; thus, red hot charcoal had evidently less power of inflamma- 
tion than red hot iron. 
