(771.) 
History of 
the inven- 
tion of the 
safety 
lamp. 
970 
be incapable of causing explosion. The former of 
these modes of protection, it was soon seen, could only 
be palliative; the only efficient form which it took, 
was that of a more effectual ventilation; but the ter- 
rific rapidity with which a mine may be suddenly in- 
vaded by fire-damp, from channels opened by a single 
blow of the pickaxe, must prevent it from ever act- 
ing as acure, The latter plan had as yet yielded 
nothing more effectual than the steel mill long used 
by miners, which produced an uncertain and inter- 
mitting light, by the rotation of a steel wheel against 
a flint, the scintillations of which were incapable of 
inflaming the fire-damp. The insufficiency of the 
light prevented it from being used, except in circum- 
stances of known danger. The celebrated Baron 
Humboldt, Dr Clanny, and several others, had in- 
vented safety-lamps on different principles; but they 
were all clumsy and more or less ineffectual.+ 
At last, in the summer of 1815, the Rey. Dr 
Gray (afterwards Bishop of Bristol), then chair- 
man of a committee appointed by a benevolent as- 
sociation at Bishop Wearmouth for the prevention of 
colliery accidents, applied to Davy, who was then on 
MATHEMATICAL AND PHYSICAL SCIENCE. 
[Diss. VI. 
carburetted hydrogen does not take fire under a per- 
fect white heat. The earliest safety-lamp consisted of 
a lantern with horn or glass sides, in which a current 
of air to supply the flame was admitted below by 
numerous tubes of small diameter, or by narrow in- 
terstices between concentric tubes of some length; or, 
finally, by rows of parallel partitions of metal, form- 
ing rectangular canals extremely narrow in propor- 
tion to their length. A similar system of escape 
apertures was applied at the top of the lantern. 
With characteristic ingenuity, Davy did not sto 
to him that wire gauze might, with equal effect, and 
far more convenience, act upon the ¢emperature of 
flame, so as to reduce it below the point of ignition, 
and thus effectually stop its communication, The ex- 
periment was successful, and by the 9th November 
1814, or within about ten weeks after his first experi- 
ments, an account of the safety-lamp defended by wire 
gauze was presented to the Royal Society. About two 
months later he produced a lamp entirely enveloped 
in metallic tissue. 
P rt?) 
here. He continued to reduce at once the apertures -~ safety 
and length of his metallic guards, until it occurred fected. 
a sporting tour in Scotland, requesting his advice and There are none of Davy’s researches which (773.) 
assistance. Sir Humphry answered the call with will stand a closer scrutiny than those which ter- Soto 
promptitude. On his southward journey, in the minated thus successfully. No fortuitous obser- for similar 
latter part of August, he visited the collieries, ascer- 
vation led him to conceive a happy idea and _ to investiga- 
tained the circumstances of the danger which he had 
apply it to,practice. A great boon to humanity tions. 
to meet, and was provided by Mr Buddle with speci- 
mens of the inflammable air for examination, Within 
a fortnight after his return to London, he had ascer- 
tained new and important qualities of the substance, 
and had already four schemes on hand for the pre- 
vention of accident. Before the end of October, he 
had arrived at the following principles of operation 
in connection with a safety-lamp. “First, A certain 
mixture of azote and carbonic acid prevents the ex- 
plosion of the fire-damp, and this mixture is neces- 
sarily formed in the safe-lantern; secondly, The fire- 
damp will not explode in tubes or feeders of a certain 
small diameter. The ingress to, and egress of air from 
my lantern,” he adds, “is through such tubes or feed- 
ers; and, therefore, when an explosion is artificially 
made in the safe-lantern, it does not communicate to 
the external air.” The effect of narrow tubes in inter- 
cepting the passage of flame, is due to the cooling effect 
of their metallic sides upon the combustible gases of 
which flame is composed ;? and one of his first and 
most important observations was the fortunate pecu- 
liarity that fire-damp, even when mixed with the 
amount of air most favourable to combustion (1 part 
of gas to 7 or 8 of air), requires an unusually high 
temperature to induce combination. Olefiant gas, 
carbonic oxide, and sulphuretted hydrogen, are all in- 
flamed by iron at a red heat, or ignited charcoal, but 
and the arts was required at his hands; and without 
a moment’s delay, he proceeded to seek for it under 
the guidance of a strictly experimental and induc- 
tive philosophy. Without, perhaps, a single false 
turn, and scarcely a superfluous experiment, he pro- 
ceeded straight to his goal, guided by the prompt- 
ings of a happy genius aided by no common industry. 
The chemical, the mechanical, and the purely physi- 
cal parts of the problem were all in turn dealt with, 
and with equal sagacity. It may safely be affirmed 
that he who was destitute of any one of these quali- 
fications must have failed in attaining the object so 
ardently desired, unless by the aid of some rare good 
fortune. We have it on Davy’s own authority, that 
none of his discoveries gave him so much pleasure 
as this one. His whole character possessed in it 
much of a sympathizing and generous humanity; 
his ideas of the dignity of science were from the first 
(as his researches in Dr Beddoes’ laboratory showed) 
intimately connected with the aim of advancing the 
welfare, and of diminishing the misfortunes of man- 
kind: the rapidity and singular success of his inves- 
tigation in the case of the safety-lamp, kept his ardent 
soul all alive, and afforded him the triumph of a Eu- 
reka at its completion, To these sources of inward 
gratification was added the unstinted meed of praise 
bestowed on him by his contemporaries. Playfair, 
1 T have spoken in Art. 393 of the independent and ingenious efforts of George Stephenson t-ards the invention of a safety- 
lamp contemporaneously with those of Davy. 
? This fact had been ascertained some years previously, by Mr Tennant and Dr Wollaston, but it remained unpublished, and 
was not applied by them to the prevention of colliery explosions. 
