st one plot in time.

"But there may be more," he warned the young inventor. "You are not
done with them yet."

The Mars was floated out of her hangar, and made ready for an ascent.
Tom, Ned, Lieutenant Marbury, Mr. Damon, and several workmen were to be
the first passengers. Tom was busy going over the various parts to see
that nothing had been forgotten.

"Well, I guess we re ready," he finally announced. "All aboard!"

"Bless my insurance policy!" exclaimed Mr. Damon. "Now that the time
comes I almost wish I wasn't going."

"Nonsense!" exclaimed Tom. "You're not going to back out at the last
minute. All aboard! Cast off the ropes!" he cried to the assistants.

A moment later the Mars, the biggest airship Tom Swift had ever
constructed, arose from the earth like some great bird, and soared
aloft.

CHAPTER XV

IN DANGER

"Well, Tom, we're moving!" cried Ned Newton, clapping his chum on the
back, as he stood near him in the pilot-house. "We're going up, old
sport!"

"Of course we are," replied Tom. "You didn't think it wouldn't go up,
did you?"

"Well, I wasn't quite sure," Ned confessed. "You know you were so
worried about--"

"Not about the ship sailing," interrupted Tom. "It was only the effect
the firing of the guns might have. But I think we have that taken care
of."

"Bless my pin cushion!" cried Mr. Damon, as he looked over the rail at
the earth below. "We're moving fast, Tom."

"Yes, we can make a quicker ascent in this than in most aeroplanes,"
Tom said, "for they have to go up in a slanting direction. But we can't
quite equal their lateral speed."

"Just how fast do you think you can travel when you are in first-class
shape?" asked Lieutenant Marbury, as he noted how the Mars was
behaving on this, the first trip.

"Well, I set a limit of seventy-five miles an hour," the young inventor
replied, as he shifted various levers and handles, to change the speed
of the mechanism. "But I'm afraid we won't quite equal that with all
our guns on board. But I'm safe in saying sixty, I think."

"That will more than satisfy the government requirements," the officer
said. "But, of course, your craft will have to come up to expectations
and requirements in the matter of armament."

"I'll give you every test you want," declared Tom, with a smile. "And
now we'll see what the Mars can do when put to it."

Up and up went the big dirigible aerial warship. Had you been fortunate
enough to have seen