ject.

"Looks like a gun," replied Mark.

"That's just what it is. It's a machine gun that will fire one hundred
shots a minute, and it can be turned in any direction, as it works on a
swivel. I don't know that we'll have any use for it, but I thought I'd
take it along."

Then the professor pointed out where the propeller shaft ran from the
engine room out through the stern, and showed how the rudder was worked
by wire ropes extending from it to the conning tower.

"In short we have everything necessary to successfully navigate the
air," he went on. "Not a thing has been overlooked. All I have to do is
to fill the big bag of oiled silk with a new gas I have discovered and
up we go. This is really the most important part of the invention.
Without this powerful gas the airship would not rise above the earth.

"But I have found this gas, which can be made in unlimited quantities
from simple materials that we can carry with us. The gas has enormous
lifting power, and if it was not for that I would not dare make such a
large and comfortable airship. As it is, we can sail through the air as
easily as if we were on an ocean liner on the sea and much more quickly.

"I generate the gas in the engine room as I need it," the professor
went on. "It goes to the oiled silk bag through two tubes. When we have
arisen to a sufficient height I start the electric engine, the propeller
whirls around, and the ship moves forward, just as a steamboat does when
the screw is set in motion. Then all I have to do is to steer."

"It's great!" cried Jack with sparkling eyes.

"It certainly is," agreed Mark.

From the stern the professor took the boys to the conning tower, where
there were several wheels and levers, that placed most of the important
machines and engines in the boat under the direct control of the
steersman. A lever turned one way would send the ship ahead. Turned in
the opposite direction it would reverse the course. A wheel like that on
an automobile served to direct the rudder and so guided the _Monarch's_
course. Other levers controlled the speed of the engines, and the supply
of gas that filled the silk bag.

"Here is where we shall carry our supplies of condensed food," the
professor went on, leading the way back into the middle room. "We will
take along capsules that will supply us in a small space with meat,
vegetables, soups, tea and coffee, besides milk.

"The water we will get as we speed along, dropping down t