242 Seientifie Labors and Character of 
of them refuse to pass to the other? Will it pass through ‘a tube? 
This brought him to the grand discovery ; for it appeared, that the 
flame of the most explosive mixture would not pass through a small 
tube,—that the communication was more easily prevented, in pro- 
portion as the tube was of a better conducting substance, and there- 
fore operated by cooling the flame below the point of kindling. It 
was only then to surround a lamp with a transparent envelop com- 
municating with the surrounding air by metallic tubes, and thus the 
air might enter freely to feed the lamp, while the flame would not be 
communicated to the surrounding atmosphere, in the most explosive 
state in which it ever could exist in a coal mine. Subsequent ex- 
periments proved, that in case the diameters of the tubes were very 
small, their lengths might be diminished to mere apertures; and 
hence it was only necessary to surround the lamp with wire gauze, 
and the air would enter freely to supply the lamp, while the flame 
could not pass through the apertures of the gauze. 
The experience of fourteen years, while the safety lamp has been 
m constant and extensive use in the coal mines of England, 
without the occurrence of a single explosion,* is the best comment 
upon the correctness of the principles which led on step by step to - 
its Construction, as well as the highest testimony in favor of the bene- 
fits which this invention has conferred upon society. We are not 
aware of any other example of a great invention so purely philosoph- 
ical as this. _ Most inventions have been partly at least the suggestion 
of accident. But here our philosopher commenced, not with con~ 
structing a lamp, but with inquiring into the nature and properties of 
the agent which he had to control. He began, like the Philis- 
tines of old, by learning where lay the secret of its might ; this beg 
discovered, it was shorn of its strength as easily as the giant of Israel. 
But he did more than simply disarm the foe: he made him his slave. 
_ Inthe most explosive mixtures, the flame of the lamp is greatly en- 
larged, and its light much augmented ; and by this change, it gives t 
the, miner instant warning of the approach of danger. é 
_ These researches on the specific nature of explosive mixtures of 
carburetted hydrogen and common air, led to the more general m- 
quiry, What isthe nature of flame? It is somewhat remarkable, 
___ that in all the researches which had been made, and the theories whielt 
_ had been proposed, on the subject of combustion, the nature of flame 
- *Graham’s Elements of Chemistry, 1829. 
