ggest cannon ever made?"

"I sure am, Ned, though I don't know that I'll make out any better than
General Waller did. It's too bad his was a failure; but I think I see
where he made some mistakes."

"Oh, you do; eh?" suddenly exclaimed a voice, and from a nearby
parapet, where he had gone to look at one of the pieces of his gun,
stepped General Waller. "So you think I made some mistakes, Tom Swift?
Where, pray?"

"In making the breech. The steel jackets were of uneven thickness,
making the strain unequal. Then, too, I do not think the powder was
sufficiently tested. It was probably of uneven strength. That is only
my opinion, sir."

"Well, you are rather young to give opinions to men who have devoted
almost all their lives to the study of high explosives."

"I realize that, sir; but you asked me for my opinion. I shall hope to
profit by your mistakes, too. That is one reason I wanted to see this
test."

"Then you are seriously determined to make a gun that you think will
rival mine."

"I am, General Waller."

"For what purpose--to sell to some foreign government?"

"No, sir!" cried Tom, with flashing eyes. "If I am successful in making
a cannon that will fire the longest shots on record, I shall offer it
to Uncle Sam first of all. If he does not want it, I shall not dispose
of it to any foreign country!"

"Hum! Well, I don't believe you'll succeed. I intend to rebuild my gun
at once, though I may make some changes in it. I am sure I shall
succeed the next time. But as for you--a mere youth--to hope to rival
men who have made this problem a life-study--it is preposterous, sir!
Utterly preposterous!" and he uttered these words much as he had
declared that it was impossible for his gun to burst, even after it was
in fragments.

"Come on, Ned," said Tom, in a low voice. "We'll go back home."

CHAPTER IX

THE NEW POWDER

"Bless my cartridge belt, Tom, you don't really mean to say that stuff
is powder!" exclaimed Mr. Damon.

"That's what I hope it will prove to be--and powerful powder at that."

"Why, it looks more like excelsior than anything else," went on the odd
man, gingerly taking up some yellowish shreds in his fingers.

"And it will burn as harmlessly as excelsior in the open air," went on
Tom. "But I hope to prove, when it is confined in a chamber, that it
will be highly explosive. I'm going to make a test of it soon."

"Give me good notice, so I can get over in the next State!" exclai