me
cannon in which it could be fired to send a projectile farther than any
cannon had ever sent one. And to do this much work was necessary.

Tom figured and planned, far into the night, for many weeks after that.
He had to begin all over again, working from the basis of the power of
his new explosive. And he had many new problems to figure out.

But finally he had constructed--on paper--a gun that was to his liking.
The most exhaustive figuring proved that it had a margin of safety that
would obviate all danger of its bursting, even with an accidental
over-charge.

"And the next thing is to get the gun cast," said Tom to Ned one day.

"Are you going to do it in your shops?" his chum asked.

"No; it would be out of the question for me. I haven't the facilities.
I'm going to give the contract to the Universal Steel Company. We'll
pay them a visit in a day or two."

But even the great facilities of the steel corporation proved almost
inadequate for Tom's giant cannon. When he showed the drawings, on
which he had already secured a patent, the manager balked.

"We can't cast that gun here!" he said.

"Oh, yes, you can!" declared Tom, who had inspected the plant. "I'll
show you how."

"Why, we haven't a mould big enough for the central core," was another
objection.

"Then we'll make one," declared Tom "We'll dig a pit in the earth, and
after it is properly lined we can make the cast there."

"I never thought of that!" exclaimed the manager. "Perhaps it can be
done."

"Of course it can!" cried Tom. "Do you think you can shrink on the
jackets, and rifle the central tube?"

"Oh, yes, we can do that. The initial cast was what stumped me. But
we'll go ahead now."

"And you can wind the breech with wire, and braze it on; can't you?"
persisted Tom.

"Yes, I think so. Are you going to have a wire-wound gun?"

"That, in combination with a steel-jacketed one. I'm going to take no
chances with 'Swiftite'!" laughed Tom, for so he had named his new
explosive, in honor of his father, who had helped him with the formula.

"It must be mighty powerful," exclaimed the manager.

"It is," said Tom, simply.

I am not going to tire my readers with the details leading up to the
casting of Tom's big cannon. Sufficient to say that the general plan,
in brief, was this: A hole would be dug in the earth, in the center of
the largest casting shop--a hole as deep as the gun was to be long.
This was about one hundred feet, thoug