172 



MATHEMATICAL AND PHYSICAL SCIENCE. 



[Diss. VI. 



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 a cure. 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. L 

 (771.) At last, in the summer of 1815, the Kev. Dr 

 History of Q ray Afterwards Bishop of Bristol), then chair- 

 tioVof the man f a committee appointed by a benevolent as- 

 safety sociation at Bishop Wearmouth for the prevention of 

 lamp. colliery accidents, applied to Davy, who was then on 

 a sporting tour in Scotland, requesting his advice and 

 assistance. Sir Humphry answered the call with 

 promptitude. On his southward journey, in the 

 latter part of August, he visited the collieries, ascer- 

 tained the circumstances of the danger which he had 

 to meet, and was provided by Mr Buddie 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 ; 2 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 



carburetted hydrogen does not take fire under a per- 

 fect ivhite 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 stop 

 here. He continued to reduce at once the apertures i amp per f 

 and length of his metallic guards, until it occurred fected. 

 to him that wire gauze might, with equal effect, and 

 far more convenience, act upon the temperature 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 

 1815, 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. 



There are none of Davy's researches which (773.) 

 will stand a closer scrutiny than those which ter- Conside r e j 1 

 minated thus successfully. No fortuitous obser- f or s i m ii aP 

 vation led him to conceive a happy idea and to investiga- 

 apply it to practice. A great boon to humanity tions - 

 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 I have spoken in Art. 393 of the independent and ingenious efforts of George Stephenson towards the invention of a safety- 

 lamp contemporaneously with those of Davy. 



2 This fact had heen ascertained some years previously, hy Mr Tennant and Dr Wollaston, but it remained unpublished, and 

 was not applied by them to the prevention of colliery explosions. 





