e
shelter. "But I think there is little danger.

"You see, the electric wires are long enough to enable him to stand
some distance from the gun. And, if he likes, he can crouch behind that
concrete wall of the next barbette. Still, there is some chance of an
accident, for, no matter how carefully you calculate the strain of a
bursting charge of powder, and how strongly you construct the
breech-block to stand the strain, there is always the possibility of a
flaw in the metal. So, Ned, I think we'll just go to the bomb-proof
ourselves, when we see General Waller making for the same place."

"I suppose," remarked Ned, "that in actual warfare anyone who fired one
of the big guns would have to stand close to it--closer than that
soldier is now."

"Oh, yes--much," replied Tom, as he watched General Waller giving the
last instructions to the private who was to press the button. "Only, of
course, in war the guns will have been tested, and this one has not.
Here he comes; I guess we'd better be moving."

General Waller, having assured himself that everything was as right as
possible, had given the last word to the private and was now making his
way toward the bomb-proof, within which were gathered his
fellow-officers and friends.

"You had better retire from the immediate vicinity of the gun," said
its inventor to Tom and Ned, as he passed them. "For, while I have
absolute confidence in my cannon, and I know that it is impossible to
burst it, the concussion may be unpleasant at such close range."

"Thank you," said Tom. "We are going to get in a safe place."

He could not refrain from contrasting the general's manner now with
what it had been at first.

As for Ned, he could not help wondering why, if the inventor had such
absolute faith in his weapon, he did not fire it himself, even at the
risk of a "concussion."

How it happened was never accurately known, as the soldier declared
positively--after he came out of the hospital--that he had not pressed
the button. The theory was that the wires had become crossed, making a
short circuit, which caused the gun to go off prematurely.

But suddenly, while Tom, Ned and General Waller were still some
distance away from the bomb-proof, there was a terrific explosion. It
seemed as if the very foundations of the fortifications would be
shattered There was a roaring in the air--a hot burst of flame, and
instantly such a vacuum was created that Tom and Ned found themselves
gaspi