“Now, Washington, you had better take the prisoner something, and get your own breakfast,” the professor said.  “I want to have a talk with the boys.”

Whistling a merry tune, the colored man took out a tray of food to Taggert, who was still bound so he could not escape.

“Now I’d like to hear your names, and all about you,” the old man said.

The lads told their simple stories from the time each of them had started to shift for himself until they had accidentally met, and been hurled from the train.

“And have you thought over what I asked you last night?” asked the professor, when they had finished.

“I have,” said Jack, “and I’d like to go along.”

“Good!  You shall go!” exclaimed the inventor.  “How about you, Mark?”

“I’ll go, too.”

“All right.  Now we have plenty to do,” the old professor went on.  “The actions of this man Taggert will hasten my plans.  There are a few finishing touches 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.