Jack opened his eyes. He turned over on one side. As he did so
Mark slowly lifted his head.

"Hello!" cried Jack, faintly.

"What's the matter?" asked Mark.

"Matter? What? Where?" inquired Mark, sitting up.

"Here! Everywhere!" replied Jack, raising himself slowly on his elbow.
"All I remember is a terrible crash. Now look at all those wheels.
Wheels! Wheels! Wheels! I wonder if they can be in my head?" and he
tried to smile.

"No, they are real wheels, and they are on the walls," announced Mark.

"Then where in the world are we?" went on Jack. "In a machine shop or a
railroad wreck?"

"Looks like--" began Mark, when he was interrupted by a voice calling:

"Hurry up, Perfessor! De boys has awakened from de unconsciousability!"

And, to the astonishment of Jack and Mark, the old man and his negro
helper hurried from the inner room and stood in front of the bed.

CHAPTER IV

THE AIRSHIP

"Do you feel better?" asked the professor, anxiously, as he came forward
and felt of the boys' pulses.

"A great deal," answered Jack. "But what has happened? Where are we?
What are all these wheels for?"

"Slowly, slowly," said the old man with a pleasant laugh. "One question
at a time. For the first: what happened was a railroad wreck."

"I remember now," said Jack, slowly. "We tried to stop the cars."

"And you didn't succeed very well," went on the old man. "However, the
sand bank did it for you, and stopped you two at the same time. As for
your second question, you are here in my shop. As to the third, those
wheels are parts of my great invention. But I will tell you about that
after a while. I must give you some medicine now, and something to eat.
Here, Washington!"

"Comin', Perfessor!"

Jack and Mark were more surprised than before when they saw a big
colored man, seemingly as strong as an ox, coming toward them with two
steaming bowls of beef broth. Washington was grinning with delight.

"Dis am de best beef stew dat eber transpositioned itself into yo'
vicinity!" he exclaimed, setting the bowls down on a table near the bed.

"Now, Washington," cautioned the old man. "No big words, remember."

"All right, Perfessor," was the answer.

"Do you boys feel like eating?" asked the aged inventor.

"I do," replied Jack. "There was a time, though, when I thought I'd
never get a chance to eat again. That was just before the crash."

"You were both knocked unconscious," the professor went on. "Washingt