button, by pressing which the power of the motor was
developed. The chief of the scientific corps then
showed him the exact point upon the scale which would
be indicated when the gun was in its proper position,
and the piece was then moved upon its bearings so
as to approximate as nearly as possible this direction.

The bow of the vessel now rose upon the swell of
the sea, and the instant that the index upon the scale
reached the desired point, the Director-in-chief
touched the button.

There was no report, no smoke, no visible sign that
the motor had left the cannon; but at that instant
there appeared, to those who were on the lookout, from
a fort about a mile away, a vast aperture in the waters
of the bay, which was variously described as from one
hundred yards to five hundred yards in diameter. At
that same instant, in the neighbouring headlands and
islands far up the shores of the bay, and in every
street and building of the city, there was felt a sharp
shock, as if the underlying rocks had been struck by a
gigantic trip-hammer.

At the same instant the sky above the spot where
the motor had descended was darkened by a wide-
spreading cloud. This was formed of that portion of
the water of the bay which had been instantaneously
raised to the height of about a thousand feet. The
sudden appearance of this cloud was even more terrible