However great the merits of Stephenson in connexion with the invention of the tube safety-lamp, they cannot be regarded as detracting from the reputation of Sir Humphry Davy. His inquiries into the explosive properties of carburetted 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 even appears that Mr. Smithson Tennant and Dr. Wollaston had observed the same fact several years before, though neither Stephenson nor Davy knew 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, have led to considerable doubts as to its safety, and to inquiries as to the means by which it may be further 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, combining the glass cylinder with the wire-gauze, was the most secure; 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.”