to put on the ship. Come out into the shed."

Delighted at the chance of helping about the mysterious _Monarch_, the
boys followed the professor. They found the shed lighted by windows in
the roof, from which the curtains had been rolled back. The windows on
the side were not opened.

By daylight the airship looked larger than before. It was a wonderful
machine. The professor and his colored helper busied themselves in the
engine room. Now and then the two boys were allowed to aid.

As he hurried about from one part of the ship to the other the professor
told them how he had come to build the _Monarch_. He said he was an old
bachelor and alone in the world, and had long desired to sail to the
north pole. The failure of many land expeditions had convinced him that
an airship was the only feasible method. Accordingly he had come to this
rather deserted part of the country, built his cabin and shed, and then
had begun the putting together of his airship.

The engine parts, the various pieces of apparatus, and the machinery, he
bought from many different sources, so as not to excite suspicion. At
last after much labor the great undertaking was done.

"The _Monarch_ has never been tested," said the professor, "but I know
it will sail. I have made many small models and they worked perfectly."

Several busy hours were spent. Much more machinery was put in the ship,
the food lockers were stored with supplies, the gasolene tanks filled,
and the supply of fur clothing increased.

"There!" exclaimed the professor at length. "We are about ready to sail.
I could start in an hour if necessary. All I have to do is to fill the
silk bag with my wonderful gas, which is all ready to generate."

"Den you'd better start to generationess it right off quicker than
sooner!" shouted Washington, running from the rear of the shed. "Hurry
up, Perfessor!"

"What's the matter?" asked Mr. Henderson anxiously.

"Dat prisoner man has escaped!" cried Washington. "He's clean gone!
Flown away! Jumped his bail!"

"That's bad!" exclaimed the professor. "He'll work some mischief now! I
guess we'll have to start on our trip at once!"

CHAPTER VI

AWAY IN THE AIRSHIP

"Quick, Washington!" cried the professor. "Jump in the engine room and
start the gas generator. Mark, you bring in from the cabin all those
wheels and things on the walls! Jack, load those packages there into the
locker in the after part of the _Monarch_! But handle them