« ПредыдущаяПродолжить »
Chap, x.] IMPROVES HIS SAFETY LAMP. 109
in a place purposely made foul as before. On this occasion, a large number of persons ventured to witness the experiments, which again proved perfectly successful. The lamp was not yet, however, so efficient as he desired. It required, he observed, to be kept very steady when burning in the inflammable gas, otherwise it was very liable to go out, in consequence, as he imagined, of the contact of the burnt air (as he then called it), or azotic gas, that lodged round the exterior of the flame. If the lamp was moved backwards and forwards the azote came in contact with the flame and extinguished it. "It struck me," said he, " that if I put more tubes in, I should discharge the poisonous matter that hung round the flame, by admitting the air to its exterior part." Although, as he afterwards explained to the Committee *, he had no access to scientific works, nor intercourse with scientific men, nor anything that could assist him in his inquiries on the subject, besides his own indefatigable spirit of inquiry, he contrived a rude apparatus by means of which he proceeded to test the explosive properties of the gas, and the velocity of current (for this was the direction of his inquiries) required to permit the explosion to pass through tubes of different diameters. His own description of these experiments, in the course of which he had several " blows up," is interesting: —
"I made several experiments (and Mr. Wood was with me at the time) as to the velocity required in tubes of different diameters, to prevent explosion from fire-damp. We made the mixtures in all proportions of light carburetted hydrogen with atmospheric air in the receiver; and we found by the experiments that when a current of the most explosive mixture that we could make was forced up a tube four-tenths of an inch in diameter, the necessary current was nine inches in a second to prevent its coming down that tube. These experiments were repeated several times. We had two or three blows up in making the experiments, by the flame getting down into the receiver, though we had a piece of very fine wire-gauze put at the bottom of the pipe, between the receiver and the pipe through which we were forcing the current. In one of these experiments I was watching the flame in the tube, my son was taking the vibrations of the pendulum of the clock, and Mr. Wood was attending to give me the column of water as I called for it, to keep the current up to a certain point. As I saw the flame descending in the tube I called for more water, and he unfortunately turned the cock the wrong way; the current ceased, the flame went down the tube, and all our implements were blown to pieces, which at the time we were not very well able to replace."
* House of Commons' Report and Evidence, ulrcady quoted, p. 10?.
The explosion of this glass receiver, which had been borrowed from the stores of the Philosophical Society at Newcastle, for the purpose of making the experiments, caused the greatest possible dismay amongst the party; and they dreaded to inform Mr. Turner, tha Secretary, of the calamity which had occurred. Fortunately none of the experimenters were injured by the explosion.
Mr. Stephenson followed up those experiments by others of a similar kind, with the view of ascertaining whether ordinary flame would pass through tubes of a small diameter; and with this object he filed off the barrels of several small keys. Placing these together, he held them perpendicularly over a strong flame, and ascertained that it did not pass upward. This served as further proof to his mind, of the soundness of the principle he was pursuing.
In order to correct the defect of his first lamp, Mr. Stephenson accordingly resolved to alter it so as to admit the air to the flame by several tubes of reduced diameter, in
Chap, x.] TESTS HIS SECOND AND THIRD LAMPS. Ill
stead of by one tube. He inferred that a sufficient quantity of air would thus be introduced into the lamp for the purposes of combustion, whilst the smallness of the apertures would still prevent the explosion passing downwards, — and at the same time, the "burnt air" (the cause, in his opinion, of the lamp going out) would be more effectually dislodged. He accordingly took the lamp to the shop of Mr. Matthews, a tinman in Newcastle, and had it altered so that the air was admitted by three small tubes inserted in the bottom of the lamp, the openings of which were placed on the outside of the burner, instead of having (as in the original lamp) one tube opening directly under the flame.
This second or altered lamp was tried in the Killingworth pit on the 4th of November, and was found to burn better than the first lamp, and to be perfectly safe. But as it did not yet come up entirely to the inventor's expectations, he proceeded to contrive a third lamp, in which he proposed to surround the oil vessel with a number of capillary tubes. Then it struck him, that if he cut off the middle of the tubes, or made holes in metal plates, placed at a distance from each other equal to the length of the tubes, the air would get in better, and the effect in preventing the communication of explosion would be the same. "I thought," he says, " that the air would have easier access, and the effect might be the same if I cut away the middle of the tubes; and that the flame, if it passed through the apertures at top, would not communicate the explosion to the hydrogen beyond the plate below. I constructed a lamp upon this principle, and found that, the holes having been punched very small, the flame never passed even through the first plate."*
Stephenson was encouraged to persevere in the completion of his safety lamp, by the occurrence of several fatal accidents about this time in the Killingworth pit. On the 9th of November, a boy was killed by a blast in the A pit, at the very place where Stephenson had made the experiments with his first lamp; and, when told of the accident, he observed that if the boy had been provided with his lamp, his life would have been saved.
* A Description of tho Safety Lamp, invented by George Stephenson, and now in use in the Killingworth Colliery. London : Baldwin, Crudock, and Joy, 1817, p. 8.
The third safety lamp, as finally designed by Stephenson, was in the hands of the manufacturer on the 24th of November, before he had heard of Sir Humphry Davy's experiments, or of the lamp which that gentleman proposed to construct. And this third lamp was finished, and tried in the Killingworth pit, on the 30th of the same month. On the 5th of December Stephenson exhibited it before the Literary and Philosophical Society of Newcastle; and shortly after it came into practical use in the Killingworth collieries. To this day it is in regular use there, under the name of the "Geordy Lamp," as contradistinguished from the " Davy; " and the Killingworth pitmen have expressed to the writer their decided preference for the " Geordy." It is certainly a strong testimony in its favour, that no accident is known to have arisen from its use, since it was first introduced into the Killingworth mines. With the addition of the wire-gauze over the glass cylinder, Mr. Stephenson expressed his conviction, before the Committee above referred to, that, so altered, his lamp is the safest for use, and superior to every other.*
* Report on Accidents in Coal Mines, 1835, p. 103.
CONTROVERSY AS TO THE INVENTION OF THE SAFETY
Although the first Safety Lamp, adapted for practical use in the every-day work of coal-mining, was contrived by George Stephenson, the name of Sir Humphry Davy, as most readers are aware, has been generally identified with the invention. But a Committee of the House of Commons, which sat in 1835, after making a careful and detailed inquiry into the whole subject, distinctly stated that " The principles of its construction appear to have been practically known to Clanny and Stephenson, previously to the period when Davy brought his powerful mind to bear upon the subject."* Not only, however, were the principles of its construction known to Stephenson, but he actually made a Lamp, the safety of which he demonstrated by repeated experiments, several months before Sir Humphry Davy had produced his Miner's Lamp, or published his views upon the subject.
Dr. Clanny had also constructed a Safety Lamp, before Stephenson had made the attempt, after a plan first suggested and tried by Humboldt. It was, to insulate the air within the lamp from the foul air in the mine, by means of water, and to keep up the supply of atmospheric air by the action of bellows. But this lamp, though safe, was found impracticable, and consequently was not adopted. What was
* Report on Accidents in Mines, Session 1835, p. vii. (Parliamentary Paper, 603.)