un-cotton in the open beat both the gun and
the gun-cotton in the reflector. This result is rendered more
important by the fact that the sound reached the Mucking Light, a
distance of 13.5 miles, against a light wind which was blowing at the
time.

Most, if not all, of our ordinary sound-producers send forth waves
which are not of uniform intensity throughout. A trumpet is loudest
in the direction of its axis. The same is true of a gun. A bell,
with its mouth pointed upwards or downwards, sends forth waves which
are far denser in the horizontal plane passing through the bell than
at an angular distance of 90 deg. from that plane. The oldest bellbangers
must have been aware of the fact that the sides of the bell, and not
its mouth, emitted the strongest sound, their practice being probably
determined by this knowledge. Our slabs of gun-cotton also emit waves
of different densities in different parts. It has occurred in the
experiments at Shoeburyness that when the broad side of a slab was
turned towards the suspending wire of a second slab six feet distant,
the wire was cut by the explosion, while when the edge of the slab was
turned to the wire this never occurred.

To the circumstance that the broadsides of the slabs faced the sea is
probably to be ascribed the remarkable fact observed on March 23, that
in two directions, not far removed from the line of fire, the
gun-cotton detonated in the open had a slight advantage over the new
gun.

Theoretic considerations rendered it probable that the shape and size
of the exploding mass would affect the constitution of the wave of
sound. I did not think large rectangular slabs the most favourable
shape, and accordingly proposed cutting a large slab into fragments of
different sizes, and pitting them against each other The differences
between the sounds were by no means so great as the differences in the
quantities of explosive material might lead one to expect. The mean
values of eighteen series of observations made on board the 'Galatea,'
at distances varying from 1.75 mile to 4.8 miles, were as follows:

Weights 4 oz. 6 oz. 9 oz. 12 oz.

Value of sound 3.12 3.34 4.0 4.03

These charges were cut from a slab of dry gun-cotton about 1.75 inch
thick: they were squares and rectangles of the following dimensions:

4 oz, 2 inches by 2 inches;

6 oz, 2 inches by 3 inches;

9 oz, 3 inches by 3 inches;

12 oz,