"At the period of this occurrence we had two kinds of safety-lamps in use in this pit, viz., 'Davy' and 'Stephenson,' and the gas, in going off to the upcast shaft, had to pass great numbers of men, who were at work with both kinds of lamps. The whole of the 'Davy's' became red-hot almost instantaneously from the rapid ignition of the gas within the gauze; the 'Stephenson's' were as instantly self-extinguished from the same cause, it being the prominent qualification of these lamps that, in addition to affording a somewhat better light than the 'Davy' lamp, they are suddenly extinguished when placed within a highly explosive atmosphere, so that no person can remain working and run the risk of his lamp becoming red-hot, which, under such circumstances, would be the result with the 'Davy' lamp. "The red-hot lamps were, most fortunately, all safely put out, although the men in many cases had their hands severely burnt by the gauze; but from that time I fully resolved to adopt the exclusive use of the 'Stephenson' lamps, and not expose men to the fearful risk they must run from working with 'Davy' lamps during the probable recurrence of a similar event. "I may remark that the 'Stephenson' lamp, originally invented by the great George Stephenson, in its present shape combines the merits of his discovery with that of Sir Humphry Davy, constituting, to my mind, the safest lamp at present known, and I speak from the long use of many hundreds daily in various collieries." In an account given in the "Times" of the 10th of August, 1867, of a number of experiments made upon different safety-lamps at the Barnsley Gas-works, occasioned by the terrible explosion at the Lund Hill Colliery, it is stated that the different lamps were tested with the following results: "The 'Davy' lamp with no shield on the outside exploded the gas in six seconds, and with the shield inside the gauze in nine seconds. The 'Belgian' lamp exploded in ten seconds; the 'Mozard' in ten seconds; the small 'Clanny' in seven seconds, the large one in ten seconds; and the 'Stephenson' in seventy-five seconds. Although the 'Stephenson' is undoubtedly the best, it will be seen that none of the so-called safety-lamps can be depended upon when coming in contact with a _strong explosive current_ of fire-damp and air." CHAPTER VII. GEORGE STEPHENSON'S FARTHER IMPROVEMENTS IN THE LOCOMOTIVE--THE HETTON RAILWAY--ROBERT STEPHENSON AS VIEWER'S APPRENTICE AND STUDENT.