osion and a shock that
knocked a couple of the men down.

"All right!" shouted Tom. "The gun held together. It's safe to go out.
We'll see what happened!"

They all rushed from the shelter of the cave. Before them was an
awe-inspiring sight. A great wall of water was coming down the valley,
from a large opening in the centre of the dam. It seemed to leap
forward like a race horse.

Tom declared afterward that he saw his projectile strike the barrier
that separated one valley from the other, but none of the others had
eyes-sight as keen as this--and perhaps Tom was in error.

But there was no doubt that they all saw what followed. They heard a
distant report as the great projectile burst. Then a wall of earth
seemed to rise up in front of the advancing wall of water. High into
the air great stones and masses of dirt were thrown.

"A good shot!" cried the foreman. "Just in the right place, Tom Swift!"

For a moment it was as though that wall of water hesitated, not
deciding whether to continue on down the populated valley, or to swing
over into the other gash where it could do comparatively little harm.
It was a moment of suspense.

Then, as Tom's great shot had, by means of the exploding projectile,
torn down the barrier, the water chose the more direct and shorter
path. With a mighty roar, like a distant Niagara, it swept into the new
channel the young inventor had made. Into the transverse valley it
tumbled and tossed in muddy billows of foam, and only a small portion
of the flood added itself to the already swollen creek.

The village of Preston had been saved by the shot from Tom's giant
cannon.

CHAPTER XX

THE GOVERNMENT ACCEPTS

"Whew! Let me sit down somewhere and get my breath!" gasped Tom, when
it was all over.

"I should think you would want a bit of quiet," replied Ned. "You've
been on the jump since early morning."

"Bless my dining-room table!" cried Mr. Damon. "I should say so! I'll
go tell the cook to get us all a good meal--we need it," for a
competent cook had been installed in the old farmhouse where Tom and
his party had their headquarters.

"But you did the trick, Tom, old man!" exclaimed Ned, fervently, as he
looked down the valley and saw the receding water. For, with the
opening of the channel into the other valley the flood, at no time
particularly dangerous near Preston, was subsiding rapidly.

"He sure did," declared the foreman. "No one else could have done it,
ei