officer went on.

"Well, if they only take it out in fear--"

"But they won't!" interrupted the officer--"They are seeking to
destroy those inventions. More than once, of late, we have nipped
a plot just in time."

"Have they really tried to damage the big gun?" asked Tom,
referring to one he had built and set up at Panama.

"They have. And now this fire proves that they are taking other
measures--they are working directly against you."

"Why, I wonder?"

"Either to prevent you from making further inventions, or to
stop you from completing your latest--the aerial warship."

"But I didn't know the foreign governments knew about that,"
Tom exclaimed. "It was a secret."

"Few secrets are safe from foreign Spies," declared Lieutenant
Marbury. "They have a great ferreting-out system on the other
side. We are just beginning to appreciate it. But our own men
have not been idle."

"Have they really learned anything?" Tom asked.
"Nothing definite enough to warrant us in acting," was the
answer of the government man. "But we know enough to let us see