th. It's sort of in the air at present. Only I don't see why a
larger gun than any that has yet been made, can't be constructed."

"If anybody can invent one, you can, Tom Swift!" exclaimed Ned,
admiringly.

"You flatter me!" exclaimed his chum, with a mock bow.

"But what good will it be?" went on Ned. "Making big guns doesn't help
any in war, that I can see."

"Ned!" exclaimed Tom, "you don't look far enough ahead. Now here's my
scheme in a nutshell. You know what Uncle Sam is doing down in his big
ditch; don't you?"

"You mean digging the Panama Canal?"

Yes, the greatest engineering feat of centuries. It is going to make a
big change in the whole world, and the United States is going to
become--if she is not already--a world-power. Now that canal has to be
protected--I mean against the possibility of war. For, though it may
never come, and the chances are it never will, still it may.

"Uncle Sam has to be ready for it. There never was a more true saying
than 'in time of peace prepare for war.' Preparing for war is, in my
opinion, the best way not to have one.

"Once the Panama Canal is in operation, and the world-changes
incidental to it have been made, if it should pass into the hands of
some foreign country--as it very possibly might do--the United States
would not only be the laughing-stock of the world, but she would lose
the high place she holds.

"Now, then, to protect the canal, several things are necessary. Among
them are big guns--cannon that can shoot a long distance--for if a
foreign nation should send some of their new dreadnaughts over
here--vessels with guns that can shoot many miles--where would the
canal be once a bombardment was opened? It would be ruined in a
day--the immense lock-gates would be destroyed. And, not only from the
guns aboard ships would there be danger, but from siege cannon planted
in Costa Rica, or some South American country below the canal zone.

"Now, to protect the canal against such an attack we need guns that can
shoot farther, straighter and more powerfully than any at present in
use, and we've got to have the most powerful explosive. In other words,
we've got to beat the biggest guns that are now in existence. And I'm
going to do it, Ned!"

"You are?"

"Yes, I'm going to invent a cannon that will make the longest shots on
record. I'm going to make a world-beater gun; or, rather, I'm going to
invent it, and have it made, for I guess it would tax this place t