struction of a gun specially
calculated to produce the loudest sound attainable from the combustion
of 3 lbs. of powder. To prevent the unnecessary landward waste of the
sound, the gun was furnished with a parabolic muzzle, intended to
project the sound over the sea, where it was most needed. The
construction of this gun was based on a searching series of
experiments executed at Woolwich with small models, provided with
muzzles of various kinds. A drawing of the gun is annexed (p. 309).
It was constructed on the principle of the revolver, its various
chambers being loaded and brought in rapid succession into the firing
position. The performance of the gun proved the correctness of the
principles on which its construction was based.

An incidental point of some interest was decided by the earliest
Woolwich experiments. It had been a widely spread opinion among
artillerists, that a bronze gun produces a specially loud report. I
doubted from the outset whether this would help us; and in a letter
dated 22nd April, 1874, I ventured to express myself thus: 'The
report of a gun, as affecting an observer close at hand, is made up of
two factors--the sound due to the shock of the air by the violently
expanding gas, and the sound derived from the vibrations of the gun,
which, to some extent, rings like a bell. This latter, I apprehend,
will disappear at considerable distances.'

FIG. 8. Breech-loading Fog-signal Gun, with Bell Mouth, proposed by
Major Maitland, R.A. Assistant Superintendent. [Footnote: The carriage
of this gun has been modified in construction since this drawing was
made.]

The result of subsequent trial, as reported by General Campbell, is,
'that the sonorous qualities of bronze are greatly superior to those
of cast iron at short distances, but that the advantage lies with the
baser metal at long ranges.' [Footnote: General Campbell assigns a
true cause for this difference. The ring of the bronze gun represents
so much energy withdrawn from the explosive force of the gunpowder.
Further experiments would, however, be needed to place the superiority
of the cast-iron gun at a distance beyond question.]

Coincident with these trials of guns at Woolwich, gun-cotton was
thought of as a probably effective sound-producer. From the first,
indeed, theoretic considerations caused me to fix my attention
persistently on this substance; for the remarkable experiments of Mr.
Abel, whereby its rapidity of combust