Stephenson's theory of the "burnt air" and the "draught" was no doubt wrong, but his lamp was right, and that was the great fact which mainly concerned him. Torricelli did not know the rationale of his tube, nor Otto von Guericke that of his air-pump; yet no one thinks of denying them the merit of their inventions on that account. The discoveries of Volta and Galvani were in like manner independent of theory; the greatest discoveries consisting in bringing to light certain grand facts, on which theories are afterward framed. Our inventor had been pursuing the Baconian method, though he did not think of that; his sole object being to invent a safe lamp, which he knew could only be done through the process of repeated experiment. Hence his numerous experiments on the fire-damp at the blowers in the mine, as well as on carbureted hydrogen gas in his cottage by means of the apparatus above described. By experiment he distinctly ascertained that the explosion of fire-damp could not pass through small tubes; and he also did what had not before been done by any inventor--he constructed a lamp on this principle, and repeatedly proved its safety at the risk of his life. At the same time, there is no doubt that it was to Sir Humphry Davy that the merit belonged of elucidating the true law on which the safety-lamp is constructed. The subject of this important invention excited so much interest in the northern mining districts, and Stephenson's numerous friends considered his lamp so completely successful--having stood the test of repeated experiments--that they urged him to bring his invention before the Philosophical and Literary Society of Newcastle, of whose apparatus he had availed himself in the course of his experiments on fire-damp. After much persuasion he consented to do so, and a meeting was appointed for the purpose of receiving his explanations on the evening of the 5th of December, 1815. Stephenson was at that time so diffident in manner and unpracticed in speech, that he took with him his friend Nicholas Wood to act as his interpreter and expositor on the occasion. From eighty to a hundred of the most intelligent members of the society were present at the meeting, when Mr. Wood stood forward to expound the principles on which the lamp had been formed, and to describe the details of its construction. Several questions were put, to which Mr. Wood proceeded to give replies to the best of his knowledge. But Stephenson, who up to that time had stood behind Wood, screened from notice, observing that the explanations given were not quite correct, could no longer control himself, and, standing forward, he proceeded in his strong Northumbrian dialect to describe the lamp down to its minutest details. He then produced several bladders full of carbureted hydrogen, which he had collected from the blowers in the Killingworth mine, and proved the safety of his lamp by numerous experiments with