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 41/2 in. in length and 11/2
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 13/4 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