SAFETY LAMP

I have reserved for this place an account of the patented improvement made upon Davy’s lamp by Me rs. Upton and Roberts; the latter of whom, having worked in coal mines from a boy, and having observed, that in peculiar circumstances, the Davy was insecure, was led to contrive certain modifications of it, for which he received, some years ago, a reward from the Society of Arts. It appears from undoubted experiments, that if a jet of carburetted hydrogen (coal gas for example) be impelled with very moderate force against the side of the Davy, it will first fill the wire cylinder of the burning lamp with flame, and then take fire itself exteriorly. This pa age of the flame of explosive gases through the meshes of wire gauze of the finene prescribed for safety lamps by Sir H. Davy, was demonstrated in several trials before the select committee of the House Commons on accidents in mines, by Mr. Pereira, at the London University. [49] While the gas is at rest, relatively to Davy’s lamp, the explosion has never been known to pa ; but “if,” says Mr. Pereira, “a lamp be held before a jet of gas until it becomes hot (a red heat is not e ential), and then gently moved, the flame will pa , and the experiment may be repeated succe ively a number of times in the minute.” Two layers of wire gauze, though they greatly impede the transmi ion of light, will still permit that of flame, in the above circumstances. In Upton and Roberts’ lamp, there is but one coat of wire gauze, but it is enclosed in a gla cylinder, in such a manner as to admit the air which feeds the flame only under its bottom, first through an annular range of holes, and next through one disc, or several, of wire gauze, fixed a little way below the wick. The explosive air, after pa ing up through these wire-gauze discs, enters a little bra cupola, and is reflected inwards from the orifice at its top upon the flame, whereby it is completely burned before it reaches the cavity of the surmounting cylinder. By this reverberatory action of the air upon the wick, the intensity of the light is at the same time greatly augmented. Since the feed orifices of the lamp are small in comparison with the capacity of the surmounting cage, the latter does not get filled with flame on being plunged in an explosive gaseous mixture, as happens to the naked cage of Davy. The wire gauze can never, therefore, become very hot, far le ignited, in the new lamp. There are, in fact, three impediments to the pa age of the flame out of the lamp; first, the stratum of carbonic acid round the light; secondly, the wire-gauze cylinder; and thirdly, the gla cylinder. The entrance at the bottom may be made secure in any desired degree, by multiplying the layers of wire cloth. The top is protected, moreover, by a bra hood, through which the currents of carbonic acid and nitrogen gases, continually ascending from the burning wick, oppose certain obstacles to the transmi ion of flame downwards. Even should the gla be accidentally broken, the lamp is still a complete Davy. [49] On the 30th of July, 1835. In the experiments made before the honourable committee at the London University, Mr. Pereira showed, first, that when a jet of coal-gas alone, or an explosive mixture of coal-gas and air, impinged upon the wire-gauze cylinder of one of Davy’s lamps with a certain force, the flame generally pa ed through the meshes, of which there were from 950 to 1024 in the square inch. When a mixture of four parts of hydrogen, and one of coal-gas was directed in a jet upon the lighted lamps of Davy, Stevens on, Dillon, Wood of Killing worth (called the refrigerating lamp), Robson, and Clanny, the flame readily pa ed; but when thrown upon the lamp of Upton and Roberts, it did not once pa , causing merely slight detonations within the lamp. When the force of the jet was augmented, it extinguished the light. This lamp was finally subjected to the still severer test of a mixture of four parts of atmospherical air, and one of hydrogen; yet it did not explode it. When exposed to a mixture of two-thirds of air, and one of hydrogen, the lamp was immediately extinguished. The following, out of many certificates, appears to me decisive in favour of this improvement of Davy’s lamp. It comes from an experienced pitman, in a very deep and extensive coal mine, which I know to be replete with explosive gas, as I have myself visited it in company with its accomplished engineer, John Buddle, Esq. “I hereby certify that I have this day tried Me rs. Upton and Roberts’ new patent safety lamp, in the Jarrow colliery; and I state, as an experienced pitman, having been thirty-two years master waste man in that colliery, that I greatly prefer this new lamp to the common Davy lamp. I had it between five and six hours on trial in the pit. I consider that it gives about three times the light of the Davy lamp, as I could see at least ten yards before me in a straight line; and of its great safety I can have no doubt, as it does not fill with flame, as the Davy does. And although I had this extra light, there was much le oil consumed. I consider it a good working lamp. “Jarrow Colliery, near Newcastle on Tyne, March 31, 1836.” (Signed) “ROBERT FAIRLY.” IMG:4147767755307473660_illo1079.png:Safety lamp Fig. 953. , is a vertical section through the middle of the lamp. a , a , is the oil-cistern, showing the fold of the wick; it is covered at top with b , b, several layers of wire gauze; c , c , is the perforated bra ring, under these layers, for admitting air, which is reverberated upon the burning wick by the cupola c ; d , d , is the cylinder of gla , surrounding the wire-cloth one; e , e , is the safety bra hood, which screws down in the frame, so as to cover in the top of the gla chimney; f , is the arched wire for suspending the lamp to the girdle of the miner; g , is the bent tube for supplying oil to the cistern; and h is the safety-trimmer, shown more distinctly in the figure illustrative of the Lamp of Davy . Between the gla and the cage there should be a space of about one-tenth of an inch, forming an annular chimney for the free ventilation of the flame; and between the under edge of the hood e , and the upper rim of the gla , there should likewise be an interval, as also vent-holes in the top of the hood, for the free escape of the smoke. The orifice of the little tube g , should be rather lower than the ring of holes c , otherwise the oil, when incautiously poured into it, might overflow them, and prevent the lamp from burning. The figure is drawn somewhat in perspective. As the naked cage of Davy often gets red-hot with flame; as it is sometimes used for hours by miners in this most hazardous state; as this lamp gives so little light as to tempt rash men to remove its safety-cage; [50] as “it is upon record, that taking the average of ten years previous to the introduction of Sir H. Davy’s safety lamp, and allowing one clear year for its introduction, and of ten years after it was properly introduced, there had been double the number of accidents, and at least double the number of deaths, of what took place in the ten years previous to its introduction; [51] as his lamp in explosive air-courses needs to be carried close upon the bosom, or under the coat of the miner; as it was declared by its illustrious inventor to be dangerous when exposed to such currents of explosive gas; and as the above described modification of it is free from all these defects and dangers,—I humbly apprehend that no conscientious proprietor or viewer of coal-mines will delay to substitute the lamp of Upton and Roberts for the naked Davy, for otherwise he will certainly stand in a very painful predicament before a coroner’s inquest, at the next mortal casualty from explosion.” [50] At Rowpit Harraton, June 30, 1817, thirty-eight lives were lost by the wilfulne of one man unscrewing it, though he was well forewarned of the danger. He said, “he could not see with that thing,” meaning the Davy.— Buddle, in Report of House of Commons , p. 215. [51] Dr. Reid Clanny, in Report on Accidents in Mines, p. 32. I observe that in Sykes’ Local Records of the counties of Durham and North umber land, corrected by J. Buddle, Esq., there are 540 deaths by explosions, between June, 1817, and June, 1835. What a ma of misery to the families of the sufferers! The patentees have, I am told, been put to so much trouble and expense in trying to introduce this life-protector into our coal-mines, that they have in a great measure abandoned the busine . Me rs. Smith of Birmingham have meanwhile undertaken to make the lamps.