“What on earth is the matter now?” demanded Chester.

Hal bent over his engine.

“I don’t know what has blown out,” he replied.  “But the engine has gone dead.”

“Dead!” exclaimed Chester.

“Yes.”

“Can you fix it?”

“Not up here.  It is impossible.  I am not familiar enough with it.”

“What shall we do, then?” cried Chester, in alarm.

“We shall have to go down.”

“What!  And land right in the middle of the German camp?”

“I am afraid so.  There is no help for it.  However, I shall sail just as far as possible before we hit the earth.”

Slowly the machine dropped, its strong planes still holding it on its forward course.  So gentle was the fall that it was almost imperceptible; but presently the distant earth below could be seen; and then Chester cried: 

“Look!  We are almost beyond the camp.  We shall clear it when we hit the ground.”

Hal glanced down.

“So we shall,” he agreed, and there was hope in his voice....  “Maybe I will be able to fix the engine before we are discovered.”

Nearer and nearer to the ground glided the huge machine.  They were now well beyond the farthest outposts of the camp, and consequently had recovered their good spirits.

The airship came gently to earth, and the boys jumped out.  As they did so, there came the faint sound of a command and a rifle cracked.

“We are discovered!” shouted Hal.  “Quick!  To the woods!” And the boys made a dash toward a clump of trees that could be seen in the distance.

Desperately the two lads ran toward the woods, and, as they ran, the first single rifle shot was followed by a volley; but, thanks to the semi-darkness, the boys gained the shelter of the woods unscathed.

Once under the friendly shelter of the trees the boys did not diminish their speed.  Rather, if possible, they ran faster.  Then, suddenly they stopped; and the cause of their abrupt halt was this: 

A heavy crashing in front of them gave evidence of the approach of a large body of men.  For a moment the lads stood as if frozen to the spot; then Hal cried: 

“Up in this tree, quick!  It’s our only chance!”

Acting upon the instant, the two lads swung themselves into the crotch of the great tree under which they stood; then climbed noiselessly higher up among the branches.  Just as they had succeeded in screening themselves from possible discovery, a body of horsemen burst in among the trees.

“Caught right in between them,” whispered Hal.

“Yes; and, if we get out of this fix alive, we are in luck,” Chester whispered back.

The horsemen below them did not pause in their march, but continued on through the woods.

“Evidently a scouting party returning,” whispered Hal.

And still the long line of horsemen pressed on beneath them.