aerial warship!" was the quiet answer.

Ned Newton gave vent to a long whistle, and then began a detailed
examination of the wonderful craft he saw before him. That is, he made
as detailed an examination as was possible under the circumstances, for
it was a long time before the young bank clerk fully appreciated all
Tom Swift had accomplished in building the Mars, which was the warlike
name painted in red letters on the big gas container that tugged and
swayed overhead.

"Tom, however did you do it?" gasped Ned at length.

"By hard work," was the modest reply. "I've been at this for a longer
time than you'd suppose, working on it at odd moments. I had a lot of
help, too, or I never could have done it. And now it is nearly all
finished, as far as the ship itself is concerned. The only thing that
bothers me is to provide for the recoil of the guns I want to carry.
Maybe you can help me with that. Come on, now, I'll explain how the
affair works, and what I hope to accomplish with it."

In brief Tom's aerial warship was a sort of German Zeppelin type of
dirigible balloon, rising in the air by means of a gas container, or,
rather, several of them, for the section for holding the lifting gas
element was divided by bulkheads.

The chief difference between dirigible balloons and ordinary
aeroplanes, as you all know, is that the former are lifted from the
earth by a gas, such as hydrogen, which is lighter than air, while the
aeroplane lifts itself by getting into motion, when broad, flat planes,
or surfaces, hold it up, just as a flat stone is held up when you sail
it through the air. The moment the stone, or aeroplane, loses its
forward motion, it begins to fall.

This is not so with a dirigible balloon. It is held in the air by means
of the lifting gas, and once so in the air can be sent in any direction
by means of propellers and rudders.

Tom's aerial warship contained many new features. While it was as large
as some of the war-type Zeppelins, it differed from them materially.
But the details would be of more interest to a scientific builder of
such things than to the ordinary reader, so I will not weary you with
them.

Sufficient to say that Tom's craft consisted first of a great
semi-rigid bag, or envelope, made of specially prepared oiled silk and
aluminum, to hold the gas, which was manufactured on board. There were
a number of gas-tight compartments, so that if one, or even if a number
of them burst, or wer