carburetted hydrogen gas were quite original; and his
discovery of the fact that explosion will not pass through tubes of a
certain diameter was made independently of all that Stephenson had done
in verification of the same fact. It even appears that Mr. Smithson
Tennant and Dr. Wollaston had observed the same fact several years
before, though neither Stephenson nor Davy knew it while they were
prosecuting their experiments. Sir Humphry Davy's subsequent
modification of the tube-lamp, by which, while diminishing the diameter,
he in the same ratio shortened the tubes without danger, and in the form
of wire-gauze enveloped the safety-lamp by a multiplicity of tubes, was a
beautiful application of the true theory which he had formed upon the
subject.

The increased number of accidents which have occurred from explosions in
coal-mines since the general introduction of the Davy lamp, have led to
considerable doubts as to its safety, and to inquiries as to the means by
which it may be further improved; for experience has shown that, under
certain circumstances, the Davy lamp is _not_ safe. Stephenson was
himself of opinion that the modification of his own and Sir Humphry
Davy's lamp, combining the glass cylinder with the wire-gauze, was the
most secure; at the same time it must be admitted that the Davy and the
Geordy lamps alike failed to stand the severe tests to which they were
submitted by Dr. Pereira, before the Committee on Accidents in Mines.
Indeed, Dr. Pereira did not hesitate to say, that when exposed to a
current of explosive gas the Davy lamp is "decidedly unsafe," and that
the experiments by which its safety had been "demonstrated" in the
lecture-room had proved entirely "fallacious."

It is worthy of remark, that under circumstances in which the wire-gauze
of the Davy lamp becomes red-hot from the high explosiveness of the gas,
the Geordy lamp is extinguished; and we cannot but think that this fact
testifies to the decidedly superior safety of the Geordy. An accident
occurred in the Oaks colliery Pit at Barnsley, on the 20th August, 1857,
which strikingly exemplified the respective qualities of the lamps. A
sudden outburst of gas took place from the floor of the mine, along a
distance of fifty yards. Fortunately the men working in the pit at the
time were all supplied with safety-lamps--the hewers with Stephenson's,
and the hurriers with Davy's. Upon this occasion, the whole of the
Stephenson's lamps, ov