lighted; and all was now ready for its trial in the pit. But Mr. Wood had not yet arrived, and it was thought necessary that he should be present. He was known to be at Benton, about a mile distant. "Robert," said George, turning to his son, "you must go over for Wood, and tell him to come directly." It was a dark night; but the boy had learnt implicitly to obey his father, and he set out forthwith. On his way he had to pass through Benton churchyard, and as he cautiously approached the wicket-gate and opened it, he thought he saw a white figure standing amongst the tombs! He started back, his heart fluttering, and, making the circuit of the wall of the burying-ground, he came round on the other side; and then he saw that the supposed white figure had been caused by a lanthorn flashing its light upon the grave-digger, who was busy plying his vocation at that late hour. Mr. Wood was soon found, and, mounting his horse, he rode over to Killingworth When Robert reached the cottage, he found his father had just left, (it was then near eleven o'clock,) and gone down the shaft for the purpose of trying the lamp in one of the most dangerous parts of the mine!

at once.

Arrived at the bottom of the shaft with the lamp, the party directed their steps towards one of the foulest galleries in the pit, where the explosive gas was issuing through a blower in the roof of the mine with a loud hissing noise. By erecting some deal boarding around that part of the gallery into which the gas was escaping, the air was thus made more foul for the purpose of the experiment. After waiting for about an hour, Moodie, whose practical experience of fire-damp in pits was greater than that of either Stephenson or Wood, was requested by them to go into the place which had thus been made foul; and, having done so, he returned, and told them that the smell of the air was such, that if a lighted candle were now introduced an explosion must inevitably take place. He cautioned Stephenson as to the danger, both to themselves and to the pit, if the gas took fire. But Stephenson declared his confidence in the safety of his lamp, and, having lit the wick, he boldly proceeded with it towards the explosive air. The others, more timid and doubtful, hung back when they came within hearing of the blower; and, apprehensive of the danger, they retired into a safe place,

out of sight of the lamp, which gradually disappeared with its bearer, in the recesses of the mine. It was a critical moment; and the danger was such as would have tried the stoutest heart. Stephenson, advancing alone, with his yet untried lamp, in the depths of those underground workings,-calmly venturing his own life in the determination to discover a mode by which the lives of many might be saved and death disarmed in these fatal caverns, presented an example of intrepid nerve and manly courage, more noble even than that which, in the excitement of battle and the collective impetuosity of a charge, carries a man up to the cannon's mouth.

Advancing to the place of danger, and entering within the fouled air, his lighted lamp in hand, Stephenson held it firmly out, in the full current of the blower, and within a few inches of its mouth! Thus exposed, the flame of the lamp at first increased, and then flickered and went out; but there was no explosion of the gas. Stephenson returned to his companions, who were still at a distance, and told them what had occurred. Having now acquired somewhat more confidence, they advanced with him to a point from which they could observe him repeat his experiment,—but still at a safe distance. They saw that when the lighted lamp was held within the explosive mixture, there was a great flame; the lamp was almost full of fire; and then it smothered out. Again returning to his companions, he relighted the lamp, and repeated the experiment. This he did several times, with the same result. At length Wood and Moodie ventured to advance close to the fouled part of the pit; and, in making some of the later trials, Mr. Wood himself held up the lighted lamp to the blower. Such was the result of the first experiments with the first practical Miner's Safety Lamp; and such the daring resolution of its inventor in testing its valuable qualities.

Before leaving the pit, Stephenson expressed his opinion that, by an alteration of the lamp, which he then contemplated, he could make it burn better. This was by a change in the slide through which the air was admitted into the lower part of the lamp, under the flame. After making some experiments on the air collected at the blower, by means of bladders which were mounted with tubes of various diameters, he satisfied himself

that, when the tube was reduced to a certain diameter, the explosion would not pass through; and he fashioned his slide accordingly, reducing the diameter of the tube until he conceived it was quite safe. In the course of about a fortnight the experiments were repeated in the pit, 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 any thing 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

* House of Commons' Report and Evidence, already quoted, p. 103.

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."

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, the 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, instead 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 fourth 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. 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." *

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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.

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

A Description of the Safety Lamp, invented by George Stephenson, and now in use in the Killingworth Colliery. London: Baldwin, Cradock, and Joy, 1817, p. 8.