Although he had then 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, Stephenson 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. In making these experiments in his cottage at the West Moor, Nicholas Wood and George's son Robert usually acted as his assistants, and sometimes the gentlemen of the neighborhood--among others, William Brandling and Matthew Bell, who were interested in coal-mining--attended as spectators. One who was present on such an occasion remembers that, when an experiment was about to be performed, and all was ready, George called to Mr. Wood, who worked the stop-cocks of the gasometer, "Wise on [turn on] the hydrogen, Nichol!" These experiments were not performed without risk, for on one occasion the experimenting party had nearly blown off the roof of the cottage. One of these "blows up" was described by Stephenson himself before the Committee on Accidents in Coal Mines in 1835: "I made several experiments," said he, "as to the velocity required in tubes of different diameters, to prevent explosion from fire-damp. We made the mixture in all proportions of light carbureted 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 Wood 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 among the party, and they dreaded to inform Mr. Turner, the secretary,[45] of the calamity which had occurred. Fortunately, none of the experimenters were injured by the accident.