Mr. Stephenson's friends then, to make assurance doubly sure, and with a view to set the question at rest, determined to take evidence in detail as to the date of discovery by George Stephenson of the fact in question, and its practical application by him in the formation and actual trial of his safety-lamp. The witnesses examined were George Stephenson himself, Mr. Nicholas Wood, and John Moodie, who had been present at the first trial of the lamp; the several tinmen who made the lamps; the secretary and other members of the Literary and Philosophical Society of Newcastle, who were present at the exhibition of the third lamp; and some of the workmen who were present at the Killingworth Colliery, who had been witnesses of Stephenson's experiments on fire-damp made with the lamps at different times before Sir Humphry Davy's investigations had been heard of. This evidence was quite conclusive to the minds of the gentlemen who investigated the subject, and they published it in 1817, together with their Report, in which they declared that, "after a careful inquiry into the merits of the case, conducted, as they trust, in a spirit of fairness and moderation, they can perceive no satisfactory reason for changing their opinion."[47] The Stephenson subscription, when collected, amounted to £1000. Part of the money was devoted to the purchase of a silver tankard, which was presented to the inventor, together with the balance of the subscription, at a public dinner given in the Assembly Rooms at Newcastle.[48] But what gave Stephenson even greater pleasure than the silver tankard and purse of sovereigns was the gift of a silver watch, purchased by small subscriptions collected among the colliers themselves, and presented to him by them as a token of their esteem and regard for him as a man, as well as of their gratitude for the perseverance and skill with which he had prosecuted his valuable and life-saving invention to a successful issue. To the last day of his life he spoke with pride of this watch as the most highly-prized gift he had ever received.
However great may be the merits of Stephenson in connection with the invention of the tube safety-lamp, they can not be regarded as detracting in any degree from the reputation of Sir Humphry Davy. His inquiries into the explosive properties of carbureted hydrogen gas were quite original, and his discovery of the fact that explosion will not pass through tubes of a certain diameter was made independently of all that Stephenson had done in verification of the same fact. It would even appear that Mr. Smithson Tennant and Dr. Wollaston had observed the same fact several years before, though neither Stephenson nor Davy knew of it while they were prosecuting their experiments. Sir Humphry Davy's subsequent modification of the tube-lamp, by which, while diminishing the diameter, he in the same ratio shortened the tubes without danger, and in the form of wire-gauze enveloped the safety-lamp by a multiplicity of tubes, was a beautiful application of the true theory which he had formed upon the subject.
The increased number of accidents which have occurred from explosions in coal-mines since the general introduction of the Davy lamp led to considerable doubts being entertained as to its safety, and inquiries were consequently made as to the means by which it might be farther improved; for experience has shown that, under certain circumstances, the Davy lamp is not safe. Stephenson was himself of opinion that the modification of his own and Sir Humphry Davy's lamp, by combining the glass cylinder with the wire-gauze, would give the best lamp. At the same time, it must be admitted that the Davy and the Geordy lamps alike failed to stand the severe tests to which they were submitted by Dr. Pereira, before the Committee on Accidents in Mines. Indeed, Dr. Pereira did not hesitate to say that, when exposed to a current of explosive gas, the Davy lamp is "decidedly unsafe," and that the experiments by which its safety had been "demonstrated" in the lecture-room had proved entirely "fallacious."
It is worthy of remark that, under circumstances in which the wire-gauze of the Davy lamp becomes red-hot from the high explosiveness of the gas, the Geordy lamp is extinguished; and we can not but think that this fact testifies to the decidedly superior safety of the Geordy. An accident occurred in the Oaks Colliery Pit at Barnsley on the 20th of August, 1857, which strikingly exemplified the respective qualities of the lamps. A sudden outburst of gas took place from the floor of the mine along a distance of fifty yards. Fortunately, the men working in the pit at the time were all supplied with safety-lamps—the hewers with Stephenson's, and the hurriers with Davy's. On this occasion, the whole of the Stephenson lamps, over a space of five hundred yards, were extinguished almost instantaneously; whereas the Davy lamps were filled with fire and became red-hot, so that several of the men using them had their hands burnt by the gauze. Had a strong current of air been blowing through the gallery at the time, an explosion would most probably have taken place—an accident which, it will be observed, could not, under such circumstances, occur from the use of the Geordy, which is immediately extinguished as soon as the air becomes explosive.[49]
Nicholas Wood, a good judge, has said of the two inventions, "Priority has been claimed for each of them—I believe the inventions to be parallel. By different roads they both arrived at the same result. Stephenson's is the superior lamp. Davy's is safe—Stephenson's is safer."
When the question of priority was under discussion at Mr. Lough's studio in 1857, Sir Matthew White Ridley asked Robert Stephenson, who was present, for his opinion on the subject. His answer was, "I am not exactly the person to give an unbiased opinion; but, as you ask me frankly, I will as frankly say, that if George Stephenson had never lived, Sir Humphry Davy could and most probably would have invented the safety-lamp; but again, if Sir Humphry Davy had never lived, George Stephenson certainly would have invented the safety-lamp, as I believe he did, independently of all that Sir Humphry Davy had done in the matter."
To this day the Geordy lamp continues in regular use in the Killingworth Collieries, and the Killingworth pitmen have expressed to the writer their decided preference for it compared with the Davy. It is certainly a strong testimony in its favor that no accident is known to have arisen from its use since it was generally introduced into the Killingworth pits.
THE STEPHENSON TANKARD.