the largest one ever made for the United States was a sixteen-inch rifled cannon—that is, it was sixteen inches across at the muzzle, and I forget just how long. It weighed many tons, however, and it now lies, or did a few years ago, in a ditch at the Sandy Hook proving grounds. It was a failure."
"And yet you are figuring on making a cannon with a muzzle thirty inches across—almost a yard—and fifty feet long and to weigh"
"No one can tell exactly how much it will weigh," interrupted Tom. "And I'm not altogether certain about the muzzle measurement, nor of the length. 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?"
