They stood about the entrance to the machine shop, talking of various topics, but they always came back to the subject of the wonderful journey before them.
Suddenly Jack, who had strolled a little away from the door, looked toward the rear of the big shed that housed the projectile, and uttered a cry. Mark heard him, and ran to his chum's side.
"Look!" exclaimed Jack, pointing to two men who were running away from the shop. "Who are those men?"
"One is that crazy machinist!" cried Mark.
"And the other is the tramp we saw looking in the window that night!" added Jack. "Come on! Let's catch them! They may have done some damage! Andy! Here! With your gun! Quick!"
The old hunter hastened to join the boys. He reached them in time to see the two intruders making for the woods back of the shed.
"Hold on there!" cried Andy, quickly raising his gun and firing over their heads.
But the men did not stop. Hardly had the echoes of Andy's weapon died away, than there sounded a loud explosion from the shop. A cloud of smoke poured from the windows.
"They've blown up the projectile!" cried Mark. "Come on!"
They ran toward the place where the explosion had occurred. As they neared the end of the shed Washington came running out. He showed great fear.