choking smoke.

No, I have the muffler cut out, and that's why she barks so. But she
runs easier that way, and I want to get her smoothed out a bit.

"Whew! That smoke!" gasped his chum. "Why don't you--whew--this is more
than I can stand," and holding his hands to his smarting eyes, Ned,
gasping and choking, staggered away to where the air was better.

"It is sort of thick," admitted Tom. "But that's only because she's
getting too much oil. She'll clear in a few minutes. Stick around and
we'll go up."

Despite the choking vapor, the young inventor stuck to his task of
regulating the motor, and in a short while the smoke became less, while
the big propeller blades whirled about more evenly. Then Tom adjusted
the muffler, and most of the noise stopped.

"Come on back, and finish pumping up the tires," he shouted to Ned. "I'm
going to stop her now, and then I'll give her the pressure test, and
we'll take a trip."

Having cleared his eyes of smoke, Ned came back to his task, and this
having been finished, Tom attached a heavy spring balance, or scales, to
the rope that held the airship back from moving when her propellers were
whirling about.

"How much pressure do you want?" asked Ned.

"I ought to get above twelve hundred With the way the motor is geared,