Scientific American Supplement, No. 620 | Page 8

at the School of Military Engineering, Chatham, to test the safety and strength of roburite, as compared with gun cotton, dynamite, and blasting gelatine. The results were conclusive of the great power of the new explosive, and so far fully confirmed the reports of the able mining engineer and the chemical experts who had been sent to Germany to make full inquiries. These gentlemen had ample opportunity of seeing roburite used in the coal mines of Westphalia, and it was mainly upon their testimony that the patents for the British empire were acquired by the Roburite Explosive Company.
It has, however, been deemed advisable to give practical proof to those who would have to use it, that roburite possesses all the high qualities claimed for it, and hence separate and independent trials have been arranged in such representative collieries as the Wharncliffe Silkstone, near Sheffield, Monk Bretton, near Barnsley, and, further north, in the Durham coal field, at Lord Londonderry's Seaham and Silksworth collieries. Mr. G.B. Walker, resident manager of the Wharncliffe Colliery Company, had gone to Germany as an independent observer--provided with a letter of introduction from the Under Secretary of State for Foreign Affairs--and had seen the director of the government mines at Saarbruck, who gave it as his opinion that, so far as his experience had gone, the new explosive was a most valuable invention. Mr. Walker was so impressed with the great advantages of roburite that he desired to introduce it into his own colliery, where he gladly arranged with the company to make the first coal mining experiments in this country. These were recently carried out in the Parkgate seam of the Wharncliffe Silkstone colliery, under the personal superintendence of the inventor, Dr. Roth, and in the presence of a number of colliery managers and other practical men.
In all six shots were fired, five of which were for the purpose of winning coal, while the sixth was expressly arranged as a "blowout shot." The roburite--which resembles nothing so much as a common yellow sugar--is packed in cartridges of about 4? in. in length and 1? in. in diameter, each containing about 65 grammes (one-seventh of a pound) inclosed in a waterproof envelope. By dividing a cartridge, any desired strength of charge can be obtained. The first shot had a charge of 90 grammes (one-fifth of a pound) placed in a hole drilled to a depth of about 4 ft. 6 in., and 1? in. in diameter. All the safety lamps were carefully covered, so that complete darkness was produced, but there was no visible sign of an explosion in the shape of flame--not even a spark--only the dull, heavy report and the noise made by the displaced coal. A large quantity of coal was brought down, but it was considered by most of the practical men present to be rather too much broken. The second shot was fired with a single cartridge of 65 grammes, and this gave the same remarkable results as regards absence of flame, and, in each case, there were no noxious fumes perceivable, even the moment after the shot was fired. This reduced charge gave excellent results as regards coal winning, and one of the subsequent shots, with the same weight of roburite, produced from 10 to 11 tons of coal in almost a solid mass.
It has been found that a fertile cause of accidents in coal mines is insufficient tamping, or "stemming," as it is called in Yorkshire. Therefore a hole was bored into a strong wall of coal, and a charge of 45 grammes inserted, and very slightly tamped, with the view of producing a flame if such were possible. This "blowout" shot is so termed from the fact of its being easier for the explosion to blow out the tamping, like the shot from a gun, than to split or displace the coal. The result was most successful, as there was no flash to relieve the utter darkness.
The second set of experiments took place on October 24 last, in the Monk Bretton colliery, near Barnsley, of which Mr. W. Pepper, of Leeds, is owner. This gentleman determined 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