1 6 Sir Humphry Davy on the fire-damp of coal mines , and on 
on by a much more powerful explosion than could possibly 
occur from the introduction of air from the mines. 
These experiments held good whatever was the propor- 
tions of the explosive mixture and whatever was the size of 
the glass vessel, (no one was ever used containing more than 
a quart) provided as many as 12 metallic tubes were used of 
y of an inch in diameter, and 2|- inches long ; or provided the 
circular metallic canals, were ~ of an inch in diameter, i.i of 
an inch deep, and at least 2 inches in circumference ; or pro- 
vided the wire gauze had apertures of only-j-^-yof an inch. When 
12 metallic tubes were employed as the medium of commu- 
nication, ~ of an inch in diameter and an inch long, the ex- 
plosion was communicated by them into the bladder. Four 
glass tubes of the of an inch in diameter and 2 inches 
long, did not communicate the explosion ; but one of this 
diameter and length produced the effect. The explosion was 
stopped by a single tube of an inch in diameter, when it 
was 3 inches long, but not when it was 2 inches long. 
The explosion was stopped by the metallic gauze of when 
it was placed between the exploding vessel and the bladder, 
though it did not present a surface of more than half a square 
inch, and the explosive mixture in the bladder in passing 
through it to supply the vacuum produced in the glass vessel, 
burnt on the surface exposed to the glass vessel for some 
seconds, producing a murmuring noise. 
A circular canal ~ of an inch in diameter, an inch and a 
* These results appear at first view contradictory to those mentioned page 9. But 
it must be kept in view that the first set of experiments were made in tubes open in 
the air, and the last in tubes exposed to the whole force of air explosion, and con- 
nected only with close vessels filled with explosive mixtures. 
