When Sir Humphrey had perfected his lamp to a point of safety he took it and went with Mr. Buddie down to Newcastle, and together they traversed with impunity some of the most dangerous parts of the Bentham seam, at that time one of the most fiery coal beds known. At about the same time the celebrated George Stephenson also invented a safety lamp similar in most respects to the Davy, so also, later, did Clanny and Museler, and all four kinds are in general use. Other styles have been invented also, but for the purposes to which a safety lamp is properly applied the Davy doubtless still excels all others. Those purposes are principally the investigation of workings to discover the presence of gas, and to aid in the erection of proper appliances for driving it out. It is not necessary, in these days of powerful ventilating machinery, to allow dangerous gases to remain in working places and to mine the coal there by the light of safety lamps. It is far safer, and better in every way, to sweep the chambers clean from foul air by strong ventilating currents, so that the miner may work by the light of his naked and most convenient common tin lamp. The objection, therefore, to the Davy lamp, that the light given out by it is too dim, need not be considered a serious one. The size of the flame cannot be increased without destroying the proportion between it and the gauze cylinder, and the size of the cylinder cannot be increased without making a dangerously large chamber for the accommodation of explosive gas. Therefore the light given out must, of necessity, be dim.