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Chap. VI. THE TUBE LAMP. 97
parties have softened down, it is not perhaps very difficult to get at the truth of this controversy. From what we have stated, we think it must be admitted that the fact that carburetted hydrogen will not explode down narrow tubes, was discovered by Stephenson, and that this fact or principle was applied by him in the invention of three successive lamps constructed under his directions. Sir Humphry Davy discovered the same fact about the same time, but most probably at a subsequent date, and afterwards constructed a safety-lamp which was preferred to that of Stephenson, on account of its greater cheapness and lightness. Sir H. Davy himself acknowledges that the merit of his lamp rested entirely on the discovery of the principle referred to, which had previously been ascertained and verified by the repeated experiments of Mr. Stephenson.
However great the merits of Mr. Stephenson in connection with the invention of the tube safety-lamp, they cannot be regarded as detracting from the distinguished reputation of Sir Humphry Davy. His inquiries into the explosive properties of carburetted hydrogen gas were quite original; and his discovery of the fact that explosion will not pass through tubes of a certain diameter was made independently of all that Stephenson had done in verification of the 6ame fact. It even appears that Mr. Smithson Tennant and Dr. Wollaston had observed the same fact several years before, though neither Stephenson nor Davy knew it while they were prosecuting their experiments. Sir Humphry Davy's subsequent modification of the tube lamp, by which, while diminishing the diameter, he in the same ratio shortened the tubes without danger, and in the form of wiregauze enveloped the safety-lamp by a multiplicity of tubes, was a beautiful application of the true theory which he had formed upon the subject.
The increased number of accidents which have occurred from explosions in coalmines since the general introduction of the Davy lamp have led to considerable doubts as to its safety, and to inquiries as to the means by which it may be
98 SUPERIOR SAFETY OF Chap. VI.
further improved ; for experience has shown that, under certain circumstances, the Davy lamp is not safe. Mr. Stephenson was of opinion that the modification of his own and Sir Humphry Davy's lamp, combining the glass cylinder with the wire-gauze, was the most secure lamp ; at the same time it must be admitted that the Davy and the Geordy lamps alike failed to stand the severe tests to which they were submitted by Dr. Pereira, when examined before the Committee on Accidents in Mines. Indeed, Dr. Pereira did not hesitate to say, that when exposed to a current of explosive gas the Davy lamp is " decidedly unsafe," and that the experiments by which its safety had been " demonstrated" in the lecture-room, had proved entirely "fallacious."
It is worthy of remark, that under circumstances in which the wire-gauze of the Davy lamp becomes red-hot from the high explosiveness of the gas, the Geordy lamp is extinguished; and we cannot but think that this fact testifies to the decidedly superior safety of the Geordy. An accident occurred in the Oaks Colliery Pit at Barnsley, on the 20th of August, 1857, which strikingly exemplified the respective qualities of the lamps. A sudden outburst of gas took place from the floor of the mine, along a distance of fifty yards. Fortunately the men working in the pit at the time were all supplied with safety-lamps—the hewers with Stephenson's, and the hurriers with Davy's. Upon this occasion, the whole of the Stephenson lamps, over a space of five hundred yards, were extinguished almost instantaneously; whereas the Davy lamps were filled with fire, and became red-hot—so much so, that several of the men using them had their hands burnt by the gauze. Had a strong current of air been blowing through the gallery at the time, an explosion would most probably have taken place,—an accident which, it will be observed, could not, under such circumstances, occur from the use of the Geordy, which is immediately extinguished as soon as the air becomes explosive.
To this day, the Geordy lamp continues in regular use in
Chap. VI. THE GEORDY LAMP. 99
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 favour, that no accident is known to have arisen from its use, since it was generally introduced into the Killingworth pits.
100 HIS CONFIDENCE IN THE LOCOMOTIVE. Chap. VII.
Fuktheb Improvements In The Locomotive — The Hetton Railway.
Mr. Stephenson's experiments on fire-damp, and his labours in connexion with the invention of the safety lamp, occupied but a small portion of his time, which was mainly devoted to the engineering business of the colliery. He was also giving daily attention to the improvement of his locomotive, which every day's observation and experience satisfied him was still far from being perfect.
At that time railways were almost exclusively confined to the colliery districts, and attracted the notice of few persons except those immediately connected with the coal trade. Nor were the colliery proprietors generally favourable to locomotive traction. There were great doubts as to its economy. Mr. Blackett's engines at Wylam were still supposed to be working at a loss; those tried at Coxlodge and Heaton, proving failures, had been abandoned; and the colliery owners, seeing the various locomotive speculations prove abortive, ceased to encourage further experiments.
George Stephenson alone remained in the field after all the other improvers and inventors of the locomotive had abandoned it in despair. He continued to entertain confident expectations of its eventual success. He even went so far as to say that it would yet supersede every other tractive power. Many looked upon him as an enthusiast, which no doubt he was, and upon sufficient grounds. As for his travelling engine, it was by most persons regarded as a curious toy; and many, shaking their heads, predicted for it " a terrible blow-up some day." Nevertheless, it was daily performing its work with regularity, dragging the Chap. VII. IMPROVEMENT OF THE RAILROAD. 101
coal waggons between the colliery and the staiths, and saving the labour of many men and horses. There was not, however, so marked a saving in the expense of working when compared with the cost of horse traction, as to induce the northern colliery masters to adopt it as a substitute for horses. How it could be improved and rendered more efficient as well as economical, was never out of Mr. Stephenson's mind. He was quite conscious of the imperfections both of the road and of the engine; and he gave himself no rest until he had brought the efficiency of both up to a higher point. He worked his way step by step, slowly but surely: every step was in advance of the one preceding, and thus inch by inch was gained and made good as a basis for further improvements.
At an early period of his labours, or about the time when he had completed his second locomotive, he began to direct his particular attention to the state of the road; as he perceived 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 travelled. 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 result was that great loss of power was caused, and also great wear and tear of machinery, by the frequent jolts and blows of the wheels against the rails. His 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