This anecdote of George Stephenson was related to the writer, near the pit-mouth, by one of the men, Kit Heppel, who had been present, and helped to build up the brick wall by which the fire was stayed, though several of the workmen were suffocated. Heppel relates that, when down the pit some days after, seeking out the dead bodies, the cause of the accident was the subject of some conversation between himself and Stephenson, and Heppel then asked him, "Can nothing be done to prevent such awful occurrences?" Stephenson replied that he thought something might be done. "Then," said Heppel, "the sooner you begin the better, for the price of coal-mining now is _pitmen's lives_." Fifty years since, many of the best pits were so full of the inflammable gas given forth by the coal that they could not be worked without the greatest danger, and for this reason some were altogether abandoned. The rudest possible means were adopted of producing light sufficient to enable the pitmen to work by. The phosphorescence of decayed fish-skins was tried; but this, though safe, was very inefficient. The most common method employed was what was called a steel mill, the notched wheel of which, being made to revolve against a flint, struck a succession of sparks, which scarcely served to do more than make the darkness visible. A boy carried the apparatus, working the wheel; and by the imperfect light thus given forth the miner plied his dangerous trade. Candles were only used in those parts of the pit where gas was not abundant. Under this rude system not more than one third of the coal could be worked, while two thirds were left. What the workmen, not less than the coal-owners, eagerly desired was a lamp that should give forth sufficient light, without communicating flame to the inflammable gas which accumulated in certain parts of the pit. Something had already been done toward the invention of such a lamp by Dr. Clanny, of Sunderland, who, in 1813, contrived an apparatus to which he gave air from the mine through water, by means of bellows. This lamp went out of itself in inflammable gas. It was found, however, too unwieldy to be used by the miners for the purposes of their work, and did not come into general use. A committee of gentlemen interested in coal-mining was formed to investigate the causes of the explosions, and to devise, if possible, some means of preventing them. At the invitation of that committee, Sir Humphry Davy, then in the full zenith of his reputation, was requested to turn his attention to the subject. He accordingly visited the collieries near Newcastle on the 24th of August, 1815, and at the close of that year, on the 9th of November, 1815, he read before the Royal Society of London his celebrated paper "On the Fire-damp of Coal Mines, and on Methods of Lighting the Mine so as to prevent its Explosion."