the Inner Circle, and sixty picked members of the Outer Circle,
chiefly mechanics and sailors, destined to be first the builders and
then the crews of the new vessels.

These, under Arnold's direction, worked almost day and night at the
task before them. Three of the air-ships were put together at a time,
twenty men working at each, and within a month from the time that the
_Avondale_ discharged her cargo, the twelve new vessels were ready to
take the air.

They were all built on the same plan as the _Ariel_, and eleven of
them were practically identical with her as regards size and speed;
but the twelfth, the flagship of the aerial fleet, had been designed
by Arnold on a more ambitious scale.

This vessel was larger and much more powerful than any of the others.
She was a hundred feet long, with a beam of fifteen feet amidships.
On her five masts she carried five fan-wheels, capable of raising her
vertically to a height of ten thousand feet without the assistance of
her air-planes, and her three propellers, each worked by duplex
engines, were able to drive her through the air at a speed of two
hundred miles an hour in a calm atmosphere.

She was armed with two pneumatic guns forward and two aft, each
twenty-five feet long and with a range of twelve miles at an altitude
of four thousand feet; and in addition to these she carried two
shorter ones on each broadside, with a range of six miles at the same
elevation. She also carried a sufficient supply of power-cylinders to
give her an effective range of operations of twenty thousand miles
without replenishing them.

In addition to the building materials and the necessary tools and
appliances for putting them together, the cargo of the _Avondale_ had
included an ample supply of stores of all kinds, not the least
important part of which consisted of a quantity of power-cylinders
sufficient to provide the whole fleet three times over.

The necessary chemicals and apparatus for charging them were also on
board, and the last use that Arnold made of the engines of the
steamer, which he had disconnected from the propeller and turned to
all kinds of uses during the building operations, was to connect them
with his storage pumps and charge every available cylinder to its
utmost capacity.

At length, when everything that could be carried in the air-ships had
been taken out of the steamer, she was towed out into deep water, and
then a shot from one of the flagship's broadsid