Scientific American Supplement, No. 620, page 19 by Various Authors
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ned to give the new explosive a fair and exhaustive trial, and the following programme was carried out in the presence of a very large gathering of gentlemen interested in coal mining. The chief inspector of mines for Yorkshire and Lincolnshire, Mr. F.N. Wardell, was also present, and the Roburite Explosives Company was represented by Lieut.-General Sir John Stokes, K.C.B., R.E., chairman, and several of the directors.
1. _Surface Experiments._--A shot fired on the ground, exposed. This gave no perceptible flame (70 grammes of roburite was the charge in these experiments).
2. A shot fired on the ground, bedded in fine coal dust. No flame nor ignition of the coal dust was perceptible.
3. A shot fired suspended in a case into which gas was conducted, and the atmospheric air allowed to enter so as to form an explosive mixture. The gas was not fired.
4. A shot fired in a boiler flue 16 ft. by 2 ft. 8 in., placed horizontally, in which was a quantity of fine coal dust kept suspended in the air by the action of a fan. No flame nor ignition of the coal dust took place.
5. A shot fired as above, except that an explosive mixture of gas and air was flowing into the boiler tube in addition to the coal dust. That this mixture was firedamp was proved by the introduction of a safety lamp, the flame of which was elongated, showing what miners call the "blue cap." There was no explosion of the gas or sign of flames.
6. A shot of roburite fired in the boiler tube without any gas or suspended coal dust. The report was quite as loud as in the preceding case; indeed, to several present it seemed more distinct.
7. A shot of ½ lb. gunpowder was fired under the same condition as No. 5, i.e., in an explosive mixture of gas and air with coal dust. The result was most striking, and appeared to carry conviction of the great comparative safety of roburite to all present. Not only was there an unmistakable explosion of the firedamp, with very loud report, and a vivid sheet of flame, but