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 were shot by an enemy,
the craft would still remain afloat.

Below the big gas bag was the ship proper, a light but strong
and rigid framework about which were built enclosed cabins. These
cabins, or compartments, housed the driving machinery, the
gas-generating plant, living, sleeping and dining quarters, and a
pilot-house, whence the ship could be controlled.

But this was not all.

Ned, making a tour of the Mars, as she swayed gently in the big
shed, saw where several aluminum pedestals were mounted, fore and
aft and on either beam of the ship.

"They look just like places where you intend to mount guns,"
said Ned to Tom.

"And that's exactly what they are," the young inventor replied.
"I have the guns nearly ready for mounting, but I can't seem to
think of a way of providing for the recoil. And if I don't take
care of that, I'm likely to find my ship coming apart under me,
after we bombard the enemy with a broadside or two."

"Then you intend to fight with this ship?" asked Ned.

"Well, no; not exactly personally. I was thinking of offering
it to the United States Government. Foreign nations are getting