which is immediately extinguished as soon as the air becomes explosive.* Nicholas Wood, a good judge, has said of the two inventions, "Priority has been claimed for each of them-I believe the inventions to be parallel. By different roads they both arrived at the same result. Stephenson's is the superior lamp. Davy's is safe-Stephenson's is safer." When the question of priority was under discussion at Mr. Lough's studio in 1857, Sir Matthew White Ridley asked Robert Stephenson, who was present, for his opinion on the subject. His answer was, "I am not exactly the person to give an unbiased *The accident above referred to was described in the "Barnsley Times," a copy of which, containing the account, Robert Stephenson forwarded to the author, with the observation that "it is evidently written by a practical miner, and is, I think, worthy of record in my father's Life." Mr. John Browne, C. E., Barnsley, in a communication which appeared in the "Times" of December 24th, 1860, observed: "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." CHAP. VI.] THE "GEORDY" SAFETY-LAMP. 197 that opinion; but, as you ask me frankly, I will as frankly say, if George Stephenson had never lived, Sir Humphry Davy could and most probably would have invented the safety-lamp; but again, if Sir Humphry Davy had never lived, George Stephenson certainly would have invented the safety-lamp, as I believe he did, independently of all that Sir Humphry Davy had done in the matter." To this day the Geordy lamp continues in regular use in the Killingworth Collieries, and the Killingworth pitmen have expressed to the writer their decided preference for it compared with the Davy. It is certainly a strong testimony in its favor that no accident is known to have arisen from its use since it was generally introduced into the Killingworth pits. CHAPTER VII. GEORGE STEPHENSON'S FARTHER IMPROVEMENTS IN THE LOCOMOTIVE -THE HETTON RAILWAY-ROBERT STEPHENSON AS VIEWER'S APPRENTICE AND STUDENT. STEPHENSON'S experiments on fire-damp, and his labors in connection with the invention of the safety-lamp, occupied but a small portion of his time, which was necessarily devoted, for the most part, to the ordinary business of the colliery. From the day of his appointment as engine-wright, one of the subjects which particularly occupied his attention was the best practical method of winning and raising the coal. Nicholas Wood has. said of him that he was one of the first to introduce steam machinery underground with that object. Indeed, the Killingworth mines came to be regarded as the models of the district; and when Mr. Robert Bald, the celebrated Scotch mining engineer, was requested by Dr. (afterward Sir David) Brewster to prepare the article "Mine" for the "Edinburg Encyclopædia," he proceeded to Killingworth principally for the purpose of examining Stephenson's underground machinery. Mr. Bald has favored us with an account of his visit made with that object in 1818, and he states that he was much struck with the novelty, as well as the remarkable efficiency of Stephenson's arrangements, especially in regard to what is called the underdip working. "I found," he says, "that a mine had been commenced near the main pit-bottom, and carried forward down the dip or slope of the coal, the rate of dip being about one in twelve; and the coals were drawn from the dip to the pit-bottom by the steam machinery in a very' rapid manner. The water which oozed from the upper winning was disposed of at the pit-bottom in a barrel or trunk, and was drawn up by the power of the engine which worked the other machinery. The dip at the time of my visit was nearly a mile in length, but has since been greatly extended. As I was considerably tired by my wanderings in the galleries, when I arrived at the CHAP. VII.] THE LOCOMOTIVE AND THE ROAD. 199 forehead of the dip, Mr. Stephenson said to me, 'You may very speedily be carried up to the rise by laying yourself flat upon the coal-baskets,' which were laden and ready to be taken up the incline. This I at once did, and was straightway wafted on the wings of fire to the bottom of the pit, from whence I was borne swiftly up to the light by the steam machinery on the pit-head." The whole of the working arrangements seemed to Mr. Bald to be conducted in the most skillful and efficient manner, reflecting the highest credit on the colliery engineer. Besides attending to the underground arrangements, the improved transit of the coals above ground from the pit-head to the shipping-place demanded an increasing share of Stephenson's attention. Every day's experience convinced him that the locomotive constructed by him after his patent of the year 1815 was far from perfect, though he continued to entertain confident hopes of its complete eventual success. He even went so far as to say that the locomotive would yet supersede every other tractionpower for drawing heavy loads. It is true, many persons continued to regard his traveling engine as little better than a dangerous curiosity; and some, shaking their heads, predicted for it "a terrible blow-up some day." Nevertheless, it was daily performing its work with regularity, dragging the coal-wagons between the colliery and the staiths, and saving the labor of many men and horses. There was not, however, so marked a saving in the expense of haulage as to induce the colliery masters to adopt locomotive power generally as a substitute for horses. How it could be improved, and rendered more efficient as well as economical, was constantly present to Stephenson's mind. He was fully conscious of the imperfections both in the road and the engine, and gave himself no rest until he had brought the efficiency of both up to a higher point. Thus he worked his way inch by inch, slowly but surely, and every step gained was made good as a basis for farther improvements. At an early period of his labors, or about the time when he had completed his second locomotive, he began to direct his particular attention to the state of the Road, perceiving that the extended use of the locomotive must necessarily depend in a great measure upon the perfection, solidity, continuity, and smoothness of the way along which the engine traveled. Even at that early period he was in the habit of regarding the road and the locomotive as one machine, speaking of the Rail and the Wheel as "Man and Wife." All railways were at that time laid in a careless and loose manner, and great inequalities of level were allowed to occur without much attention being paid to repairs. The consequence was a great loss of power, as well as much wear and tear of the machinery, by the frequent jolts and blows of the wheels against.the rails. Stephenson's first object, therefore, was to remove the inequalities produced by the imperfect junction between rail and rail. At that time (1816) the rails were made of cast iron, each rail being about three feet long; and sufficient care was not taken to maintain the points of junction on the same level. The chairs, or cast-iron pedestals into which the rails were inserted, were flat at the bottom, so that whenever any disturbance took place in the stone blocks or sleepers supporting them, the flat base of the chair upon which the rails rested being tilted by unequal subsidence, the end of one rail became depressed, while that of the other was elevated. Hence constant jolts and shocks, the reaction of which very often caused the fracture of the rails, and occasionally threw the engine off the road. To remedy this imperfection, Mr. Stephenson devised a new chair, with an entirely new mode of fixing the rails therein. Instead of adopting the butt-joint which had hitherto been used in all cast-iron rails, he adopted the half-lap joint, by which means HALF-LAP JOINT. the rails extended a cer- rest apex of a curve forming the bottom of the chair. The supports were also extended from three feet to three feet nine inches or four feet apart. These rails were accordingly substituted for the old castiron plates on the Killingworth Colliery Railway, and they were found to be a very great improvement on the previous system, |