"I would, indeed, Tom. Have you made your big gun yet?"
"No, but I am working on the plans. I want first to decide on the kind of explosive I am to use, so I can make my gun strong enough to stand it."
"A wise idea. I think there is where I made my mistake. I did not figure carefully enough on the strength of material. The internal pressure of the powder I used, as well as the muzzle velocity of my projectile, were both greater than they should have been. Take a lesson from my failure. But I am going to start on another gun soon, and—Tom Swift—I am going to try to beat you!"
"All right, General," answered Tom, genially. "May the best gun win!"
"Bless my powder box!" cried Mr. Damon. "That's the way to talk."
General Waller was much interested in going about Tom's shop, and expressed his surprise at the many inventions he saw. While ordnance matters, big guns and high explosives were his hobby, nevertheless the airships were a source of wonder to him.
"How do you do it, Tom?" he asked.
"Oh, by keeping at it," was the modest answer. "Then my good friends here—Ned and Mr. Damon—help me."
"Bless my check book!" exclaimed the odd gentleman. "It is very little help I give, Tom."
General Waller soon took his departure, promising to call again, to see Tom's test if one were held. He also repeated his determination to set the Secret Service men at work to discover the mysterious German.