CHAPTER XI

"N. A. L."


"Stolen!" exclaimed Dave, in dismay.

"It startles you?" spoke the manager of the Interstate Aeroplane
concern. "So it did us."

"But--"

"You are mystified--unusual occurrence rather. You can follow the
track of a stolen automobile. But when it comes to pursuing an
airship, you won't find many familiar roads in the clouds."

"How did it happen?" inquired Dave.

"Why, we had tested the machine and it was to have been shipped to
you yesterday. The day before, our expert made a very fine and
satisfactory demonstration. The tanks were full, everything in
perfect shape for another spurt early yesterday morning. During the
night some one scaled the fence, evaded the watchman, and broke into
the aerodrome."

"It must have been some one familiar with the place here," suggested
Dave.

"We don't know that. It is certain, though, that they knew all
about airships."