"That's it!" shouted the foreman. "Fire!"
Tom pressed the button. Once again was that awful tremor of the earth—the racking shake—the terrific explosion 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
