make you feel that way?" asked the
lieutenant.

"Well, not exactly; it is more their bearing, and the manner in which
they go about the works. I must keep my eye on them, for it takes only
a few discontented men to spoil a whole shop full. I will be on my
guard."

"And not only about your new airship and other inventions," said the
officer, "but about yourself, personally. Will you do that?"

"Yes, though I don't imagine anything like that will happen."

"Well, be on your guard, at all events," warned Lieutenant Marbury.

As Tom had said, he had been obliged to hire a number of new men. Some
of these were machinists who had worked for him, or his father, on
previous occasions, and, when tasks were few, had been dismissed, to go
to other shops. These men, Tom felt sure, could be relied upon.

But there were a number of others, from New York, and other large
cities, of whom Tom was not so sure.

"You have more foreigners than I ever knew you to hire before, Tom,"
his father said to him one day, coming back from a tour of the shops.

"Yes, I have quite a number," Tom admitted. "But they are all good
workmen. They stood the test."

"Yes, some of them are too good," observed the older inventor. "I saw
one of them making up a small motor the other day, and he was winding
the armature a new way. I spoke to him about it, and he tried to prove
that his way was an improvement on yours. Why, he'd have had it
short-circuited in no time if I hadn't stopped him."

"Is that so?" asked Tom. "That is news to me. I must look into this."

"Are any of the new men employed on the Mars?" Mr. Swift asked.

"No, not yet, but I shall have to shift some there from other work I
think, in order to get finished on time."

"Well, they will bear watching I think," his father said.

"Why, have you seen anything--do you--" began the young man, for Mr.
Swift had not been told of the suspicions of the lieutenant.

"Oh, it isn't anything special," the older inventor went on. "Only I
wouldn't let a man I didn't know much about get too much knowledge of
my latest invention."

"I won't, Dad. Thanks for telling me. This latest craft is sure going
to be a beauty."

"Then you think it will work, Tom?"

"I'm sure of it, Dad!"

Mr. Swift shook his head in doubt.

CHAPTER XI

A DAY OFF

Tom Swift pondered long and intently over what his father had said to
him. He sat for several minutes in his private office, after the aged