"Perfesser wants yo' immediate," said Washington.

"But we haven't caught a single fish," objected Mark.

"Them's the orders from headquarters," replied the colored man. "Yo'
both got t' project yo'selves in th' vicinity of th' machine shop. I
reckon th' new fangled contraption that th' perfesser is goin' t'
navigate th' air an' sail th' angry seas in, am about done. He want's
t' try th' engine."

"Come on then," said Jack. "We probably would not catch any fish,
anyhow, Mark."

Accompanied by Washington, the youths, each of whom was about eighteen
years old, started toward the big shed.

While they are on their way opportunity may be taken to tell a little
about them, as well as about Washington and the professor, and the
curious craft on which the scientist was working.

A few years before this story opens Mr. Henderson had invented a
wonderful electric airship. He had it about completed when, one day,
he and the two boys became unexpectedly acquainted, and, as it
developed, friends.

Mark and Jack were orphans. After having rather a hard time knocking
about the world trying to make a living, they chanced to meet, and
resolved to cast their lots together. They boarded a freight train,
and, as told in the first volume of this series, entitled, "Through
the Air to the North Pole; or the Wonderful Cruise of the Electric