for a distance of nearly 2 ft. The report was very loud, and a
trumpet-shaped orifice was formed at the mouth of the hole, but no
flame or spark could be perceived, nor was any inconvenience caused by
the fumes, even the instant after the explosion.

_Further Experiments at Wharncliffe Colliery._--On Tuesday, October
25, some very interesting surface trials were arranged with great care
by Mr. Walker. An old boiler flue was placed vertically, and closed at
top by means of a removable wooden cover, the interior space being
about 72 cubic feet. A temporary gasometer had been arranged at a
suitable distance by means of a paraffin cask having a capacity of 6
cubic feet suspended inside a larger cask, and by this means the
boiler was charged with a highly explosive mixture of gas and air in
the proportion of 1 to 12.

1. A charge of gunpowder was placed in the closed end of a piece of
gas pipe, and strongly tamped, so as to give the conditions most
unfavorable to the ignition of the firedamp. It was, however, ignited,
and a loud explosion produced, which blew off the wooden cover and
filled the boiler tube with flame.

2. Under the same conditions as to firedamp, a charge of roburite was
placed on a block of wood inside the boiler, totally unconfined except
by a thin covering of coal dust. When exploded by electricity, as in
the previous case, no flame was produced, nor was the firedamp
ignited.

3. The preceding experiment was repeated with the same results.

4. A charge of blasting gelatine, inserted in one of Settle's water