Scientific American Supplement, No. 620 | Page 8

coal has been carried out
during the last ten days in the South Yorkshire coal field. The new
mines regulation act provides that any explosible used in coal mines
shall either be fired in a water cartridge or be of such a nature that it
cannot inflame firedamp. This indeed is the problem which has puzzled

many able chemists during the last few years, and which Dr. Roth, of
Berlin, claims to have solved with his explosive "roburite." We recently
gave a detailed account of trials carried out 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 4½ in. in length and 1½

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 1¾ 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