aptive balloon of my craft, and see how she behaves. I don't
want to take too many chances with that new recoil check, though it
seems to work perfectly in theory."

The day came when, for the first time, the Mars was to come out of the
big shed where she had been constructed. The craft was not completed
for a flight as yet, but could be made so in a few days, with rush
work. The roof of the great shed slid back, and the big envelope
containing the buoyant gas rose slowly upward. There was a cry of
surprise from the many workmen in the yard, as they saw, most of them
for the first time, the wonderful new craft. It did not go up very
high, being held in place with anchor ropes.

The sun glistened on the bright brass and nickel parts, and glinted
from the gleaming barrels of the quick-firing guns.

"That's enough!" Tom called to the men below, who were paying out the
ropes from the windlasses. "Hold her there."

Tom, Ned, Lieutenant Marbury and Mr. Damon were aboard the captive Mars.

Looking about, to see that all was in readiness, Tom gave orders to
load the guns, blank charges being used, of course.

The recoil apparatus was in place, and it now remained to see if it
would do the work for which it was designed.

"All ready?" asked the young inventor.

"Bless my accident insurance policy!" exclaimed Mr. Damon. "I'm as
ready as ever I shall be, Tom. Let 'em go!"

"Hold fast!" cried Tom, as he prepared to press the electrical switch
which would set off the guns. Ned and Lieutenant Marbury stood near the
indicators to notice how much of the recoil would be neutralized by the
check apparatus.

"Here we go!" cried the young inventor, and, at the same moment, from
down below on the ground, came a warning cry:

"Don't shoot, Massa Tom. Don't shoot! Mah mule, Boomerang--"

But Eradicate had spoken too late. Tom pressed the switch; there was a
deafening crash, a spurt of flame, and then followed wild cries and
confused shouts, while the echoes of the reports rolled about the hills
surrounding Shopton.

CHAPTER X

THE NEW MEN

"What was the matter down there?"

"Was anyone hurt?"

"Don't forget to look at those pressure gauges!"

"Bless my ham sandwich!"

Thus came the cries from those aboard the captive Mars. Ned, Lieutenant
Marbury and Tom had called out in the order named. And, of course, I
do not need to tell you what remark Mr. Damon made. Tom glanced toward
where Ned and the government man