go higher?"

"No-no-I-I guess not," was Tom's answer. He halted over the works, and
his breath came in gasps.

"Don't get alarmed," called Mr. Sharp quickly, noting that his
companion was in distress because of the high altitude. "That always
happens to persons who go into a thin air for the first time; just as
if you had climbed a high mountain. Breathe as slowly as you can, and
swallow frequently. That will relieve the pressure on your ear drums.
I'll send the ship lower."

Tom did as he was advised, and the aeronaut, deflecting the rudder,
sent the Red Cloud on a downward slant. Tom at once felt relieved,
both because the action of swallowing equalized the pressure on the
ear drums, and because the airship was soon in a more dense
atmosphere, more like that of the earth.

"How are you now?" asked the man of the lad, as the craft was again on
an even keel.

"All right," replied Tom, briskly. "I didn't know what ailed me at
first."

"I was troubled the same way when I first went up in a balloon,"
commented Mr. Sharp. "We'll run along for a few miles, at an elevation
of about five hundred feet, and then we'll go to within a hundred feet
of the earth, and see how the Red Cloud behaves under different
conditions. Take a look below and see what you think of it."