A description of the Safety Lamp, &c.

Several of my friends having expressed a wish that I would lay an engraved plan of my Safety Lamp before the public, with as correct an account of the dates of the invention as I am able, I have resolved to do so. I was, at the same time, advised to publish the steps by which I was led to this discovery, and the theory I had formed in my own mind upon the subject, which, with the facts from which I drew my conclusions, were freely communicated to several persons during the time I was engaged in the pursuit. With this I cannot persuade myself to comply ; mt habits, as a practical mechanic, make me afraid of publishing theories, and I am by no means satisfied that my own reasons, or any of those I have seen published, why hydrogen gas will not explode through small apertures, are the true ones. It is sufficient for our present purpose that that fact has been discovered, and that is has been successfully applied in the construction of a Lamp that may be carried with perfect safety into the most explosive atmosphere.

During the four years that I have been employed to superintend the engines at Killingworth Colliery, one of the most extensive mines in Northumberland, where there is a considerable quantity of machinery under ground, I have had frequent opportunities of employing my leisure hours in making experiments upon hydrogen gas : the result of these experiments has been the discovery of the fact above stated, and the consequent formation of a Safety Lamp, which has been, and is still, used in that concern, and which my friends consider, (with what justice the public must decide,) as precisely the same in principle with that subsequently presented to their notice by Sir Humphrey Davy. A plan of that gentleman's Lamp I shall take the liberty of adding, with the time of its arrival in this part of the country, and some dates I have extracted from a letter published by the Rev. John Hodgson, and from the Newcastle Chronicle. The use of the wire gauze is certainly a happy application of a beautiful manufacture to a very useful purpose, but I confess I cannot consider it in any other light than as a variation in construction. If any other substance was to be used instead of the glass cylinder, for instance, the tin guard in plate 3, fig. 2, it surely must have been immediatley obvious that no apertures could be allowed in it greater than those through which I had ascertained explosion would not pass. As a discovery, the person who first constructed the perforated Tin Lanthorn in common use, may, with great justice, claim the merit of having surrounded the flame with a substance less liable to injury than glass, which, at the same time that it admits the air, transmits the light. it might be considered a want of candour were I not to take notice of the Lamp constructed by Dr. Clanny, but my reason for not inserting it is, that I considered it as constructed upon a principle entirely different from mine, that of separating the external and internal hydrogen my means of water. If I am deceived, there can be no question upon the merit of the discovery, as there is no doubt but that gentleman had directed his talents to the subject, and had constructed his original Lamp long before I had reduced my ideas into practice.

With respect to Mr. R. W. Brandling and Mr. Murray's Lamps, I conceive them to have been constructed on the principle of not allowing the hydrogen gas, in any gas, to come in contact with the flame, which they proposed to accomplish by means of flexible tubes. At least, this I know was the intention of the former gentleman, — whose more complex machine, to which the Lamp was in some cases to be attached, was intended to meet the danger arising from carbonic acid gas, and hydrogen gas, the date of which invention may be easily ascertained, by its having been published soon after a very melancholy accident that occurred in one of the mines in this country.

I shall now proceed to describe the Lamps I constructed.
 

Plate 1  Fig. 1 A. B. C. D. the lamp made of tin. G. the glass cylinder. A. E. F. D. the top which takes off to admit the glass cylinder, and keeps it tight to the bottom B.C. H. two tin tubes, the cavity between them for the wick ; the interior one to admit the air. I. the chamber for the oil.   Fig. 3 K. The bottom of the lamp with the slide P. to regulate the quantity of air to be admitted.   Fig. 2 L. M. N. O. the case in which the lamp is carried, with the tin back (which in fig. 1. is seen through the glass at G.) turned towards the opening where the light is not required. This Lamp was tried in Killingworth Colliery, on the 21st of October, 1815. The idea I had long entertained, and the drawing was shewn to several persons employed in that concern, two months before the day above mentioned, when, I carried it with safety into a part of the mine where a strong blower of hydrogen was coming off. An experiment which was immediately repeated in the presence of two persons employed in that concern.

 

Plate 2  Fig. 1 A. B. C. D. the lamp. E. Three small tubes passing through the oil vessel, and out at bottom B.C. to admit the air to the flame. F. the tube for the wick. G. a small wire to raise and trim the wick. Fig. 2 H. I. K. L. the cover to protect the glass cylinder. Fig. 3 M. the bottom of the lamp shewing the three apertures, and the wire to trim the wick. This was ordered immediately after the former one had been tried ; and, on the 4th of November, was exposed to a blower in the same mine. — it was found to burn considerably better, and to be perfectly safe ; but as it did not entirely answer my expectations, I determined to surround the oil vessel with a number of capillary tubes, as shewn ny the section, fig. 3, plate 3, in which the case apertures would present the same appearance as the perforations in fig. 1, in the same plate ; but I thought that the air would have an easier access, and that the effect might be the same if I cut away the middle of the tubes; and that the flame, if it passed through the apertures at the top would not communicate the explosion to the hydrogen beyond the plate below. I constructed a Lamp upon this principle, and found that the holes having been punched very small, the flame never passed even through the first plate.

 

Plate 3 Fig. 1 A. B. C. D. the lamp. A. E. F. D. the cover for the top. G. the tube for supplying the oil. H. the wire to trim the wick. I. the perforated plate covering the air chamber which surrounds the oil vessel. K. L. apertures through which the air passes into the air chamber. M. tube for the wick. Fig. 2 N. O. P. Q. the cover to protect the glass cylinder. Fig. 3 A. B. C. D. a section of the lamp. a. b. c. d. the capillary tubes. E. F. the apertures answerinf to the round holes in plate 3, fig. 1. The second plate, which is not shewn in fig. 1, corresponds with the apertures at c. d. fig. 3. This plate represents the Lamp at present in Killingworth Colliery. One, similar in principle and in construction (except that the top of the glass was contracted into a conical form), was in the hands of the manufacturer at the time I exhibited my former one to Mr. R. W. Brandling and Mr. Murray of Henderland, on the 24th of November, and was tried in the mine on the 30th, and on the 5th December was exhibited before the Literary and Philosophical Society of Newcastle.

 

Plate 4, represents Sir Humphrey Davy's Lamp Fig. 1. represents a wire gauze safe-lamp of exactly half the length and breadth of a working lamp. A. the cistern which contains the oil. B. the rim in which the wire gauze cover is fixed, and which is fastened to the cistern by a moveable screw. C. an aperture for supplying oil, fitted with a screw or a cork, and which communicates with the bottom of the cistern by a tube. D. the receptacle for the wick. E. a wire for raising, lowering, or trimming it, and which passes through a safe tube. F. the wire gauze cylinder, which should not have less than 625 apertures to the square inch. G. the second top ? of an inch above the first. H. a copper plate, which may be in contact with the second top. I. I. I. I. thick wires surrounding the cage to preserve it from being bent. K. K. are rings to hold or hang it by.