ave been impossible, but,
ever since the success of the experiment at Potsdam, German engineering
firms had been working hard under John Castellan's directions turning
out improved models of the _Flying Fish_. The various parts were
manufactured at great distances apart, and no one firm knew what the
others were doing. It was only when the parts of the vessels and the
engines were delivered at the closely-guarded Imperial factory at
Potsdam, that, under Castellan's own supervision, they became the
terrible fighting machines that they were.

The Aerial Fleet numbered twenty when war broke out, and of these five
had been detailed for the attack on Dover. They were in fact the
elements which made that attack possible, and, as is already known, four
were co-operating with the Northern Division of the Allied Fleets
against the forts defending Chatham and London.

Dover was at that time one of the most strongly fortified places in the
world. Its magnificent new harbour had been completed, and its
fortifications vastly strengthened and re-armed with the new
fourteen-inch gun which had superseded the old sixteen-inch gun of
position, on account of its greater handiness, combined with greater
penetrating power.

But at Dover, as at Portsmouth, the forts were powerless against the
assaults of these winged demons of the air. They were able to use their
terrible projectiles with reckless profusion, because only twenty-two
miles away at Calais there were inexhaustible stores from which they
could replenish their magazines. Moreover, the private factory at Kiel,
where alone they were allowed to be manufactured, were turning them out
by hundreds a day.

They had, of course, formed the vanguard of the attacking force which
had advanced in three divisions in column of line abreast from Boulogne,
Calais and Antwerp. The Boulogne and Calais divisions were French, and
each consisted of six battleships with the usual screens of cruisers,
destroyers and torpedo boats: these two divisions constituted the French
North Sea Squadron, whose place had been taken by the main German Fleet,
assisted by the Belgian and Dutch squadron.

Another German and Russian division was advancing on London. It included
four first-class battleships, and two heavily-armed coast defence ships,
huge floating fortresses, rather slow in speed, but tremendous in power,
which accompanied them for the purpose of battering the fortifications,
and doing as much damage