footsteps were heard outside. Then the noise of some persons on the roof
was audible. In a few minutes Washington came in.

"I found three men," explained the negro. "One is dat old hunter as
helped us before, Andy Sudds. He was goin' huntin' but he said he'd help
take the roof off fer a dollar. De oder two is does farm hands, Tom
Smith an' Bill Jones. Dey was goin' down to do post-office, but dey said
dey'd help fer fifty cents apiece. All three is up on de roof now."

"Good!" exclaimed the professor. "It's lucky I had the roof made in
sections when I built this shed. Now it can be taken off in a hurry.
Come on, boys! There are some more things that must go in the ship!"

Thus urged, Mark and Jack worked with a will. Washington helped, and
then went up on the roof to aid the three emergency toilers. By this
time several sections of the covering to the shed had been taken off and
the place was quite light.

All the while the gas machine in the ship continued to generate the
vapor. It flowed into the cigar-shaped bag through two rubber tubes. As
the bag distended more and more, the _Monarch_ tugged and pulled at the
anchoring ropes on the floor of the shed, as if anxious to be away.

The boys worked with a will. The last articles were placed in the
various rooms of the airship's cabin, until the balloon shed was
stripped quite bare. The professor was busy in the engine room. The
noise of the gas generating machine increased.

Then came a series of sharp explosions as one of the gasolene engines
was started. This was followed by the hum of an electric dynamo, and the