"And 'flowed' is a mighty good word, Wash," chuckled Jack. "Ah! here
is the professor, Mark."

Professor Henderson was an aged man with snow white hair and beard.
Although he was not physically as strong as he once was, his brain and
energy were not in the least impaired by advancing years. He had taken
the two lads, Jack Darrow and Mark Sampson, both orphans, under his
care some years before, and under his tuition and by his aid they were
much farther advanced in knowledge of the practical sciences than other
boys of their age.

The professor welcomed them cordially and at their request gave a
thorough scrutiny to the various mechanical contrivances that went to
the make-up of the flying machine. He pronounced it, as far as could
be known before a practical test, a perfect mechanism.

"And we will try it to-morrow morning, boys," he said, with almost as
much enthusiasm as Jack and Mark themselves displayed. "You have
completed the machine in excellent time, and I "un likewise ready to
make the experiment."

"What experiment, Professor?" asked the boys in chorus.

"Haven't you noticed what I was tinkering on at the other end of the
shop?" queried Professor Henderson, in surprise.

"Why, I see that you have a long steel plank there, with some kind of
a compressed air contrivance at one end," said Jack.

"Is that what you mean, Professor?" queried Mark.