antly by a report like that of a thousand cannons. The locomotive
came to a stop with a jolt as Hal applied the brakes.

"What's up now?" demanded Chester.

"I don't know; but that explosion sounded to me as if there were
something wrong ahead. I wouldn't be surprised if the Germans had
dynamited the bridge."

"By George! I believe you are right," exclaimed Chester. "I wouldn't
have thought of it, and if I had been in your place at the throttle
the chances are we would have gone over if such is the case."

"Well," said Hal, "I'll climb down, take a walk ahead and
investigate."

"I'll go with you," declared Chester.

"No, you won't. You stay here and watch the engine."

"You are right, as usual," said Chester. "But don't be any longer than
you can help."

Hal agreed, and a moment later Chester lost sight of him in the
darkness.

Slowly and cautiously Hal made his way along the track. As he moved
stealthily around a curve in the road the cause of the explosion
became apparent. It was even as he had feared. His quick wit had
detected the meaning of the explosion and none too soon.

Just ahead, where a short time before had been a bridge spanning a
deep chasm, there was now nothing but space. The bridge had been blown
up. Had Hal applied the brakes to the engine one minute later, in
spite of the fact that it was traveling very slowly, both boys
probably would have been carried over the embankment to certain death;
for it is doubtful that either, in the darkness, would have noticed
the absence of the bridge in time to leap to safety.

And now Hal could make out a number of rapidly moving figures. To his
dismay, he saw that they were moving in his direction. He turned
quickly and ran back to the locomotive, where Chester was anxiously
awaiting his return.

"Out here, quick!" he cried, and Chester, in response to his command,
leaped to the ground.

Hal once more jumped aboard the locomotive, unheeding Chester's cry of
wonder, released the brakes, and threw the throttle wide open. Then he
dropped sprawling to the ground, while the engine dashed madly down
the track.

Hal was not badly hurt and was quickly on his feet.

"What's the matter?" asked Chester in alarm.

"Matter is that the Germans are coming this way," answered Hal. "Come,
let's get away from here while we have a chance. We may be able to
escape in the darkness."

"But why did you start that engine down the track like that?"

"Well, I couldn'