Page:Tom Swift and His Giant Cannon.djvu/102

92 do not know how long I shall remain in this vicinity. If I knew where to look for the German I would make a careful search. As it is, I shall turn this letter over to the United States Secret Service, and see what its agents can do. And, Tom, if you are annoyed again, let me know. You are a sort of rival, so to speak, but, after all, we are both working to serve Uncle Sam. I'll do my best to protect you."

"Thank you, sir," replied Tom. "On my part, I shall keep a good lookout. It will be a bold spy who gets near my shop after this. I'm going to put up my highly-charged protecting electric wires again. We were just talking about them when you came in. Would you like to look about here, General?"

"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