working men, who are usually well
informed on many other points, that the commercial failure of these
machines is due to their opposition. In connection with colliery
work, and indeed in connection with explosives, in the sense of a
substitution for them of sources of expansion acting more slowly,
mention should be made of the hydraulic wedges. The employment of
these in lieu of gunpowder, to force down the block of coal that had
been undercut, is one of the means to be looked to for diminishing the
explosions in collieries. Another substitute for gunpowder is found in
the utilization of the expansion of lime when wetted. This has given
birth to the lime cartridge, the merits of which are now universally
recognized, but it is feared that trade prejudices may also prevent
its introduction. While on this subject of "accidents in mines," it
will be well to call attention to the investigations that have been
made into the causes of these disasters, and into the probable part
played by the minute dust which prevails to so great an extent in dry
collieries.

The experiments of our honorary member, Sir Frederick Abel, on this
point have been of the most striking and conclusive character, and
corroborate investigations of the late Macquorn Rankine into the
origin of explosions in flour mills and rice mills, which had
previously been so obscure. The name of Mr. Galloway should also be
mentioned as one of the earliest workers in this direction. At
first sight, pile driving appears to have but little connection with
explosives, but it will be well to notice an invention which has been
brought into practical use, although not largely (in this country at
all events), for driving piles, by allowing the monkey to fall on
a cartridge placed in the cavity in the cap on top of the pile; the
cartridge is exploded by the fall, and in the act of explosion drives
down the pile and raises the monkey; during its ascent, and before the
completion of its descent, time is found for the removal of the empty
cartridge and the insertion of a new one.

CANALS AND RIVER IMPROVEMENTS.

In the days of Brindley and of Smeaton, and of the other fathers
of our profession, whose portraits are on these walls, canals and
canalized rivers formed the only mode of internal transit which was
less costly than horse traction, and, thanks to their labors, the
country has been very well provided with canals; but the introduction
of railways proved, in the first