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.