“Isn’t this as good a place as any?” asked Joe.  “If we go on any farther we may get into a hole we can’t get out of.  I say, let’s stay here.  We’ll be safe from the airship bombs.”

“I don’t know about that,” said Blake.  “If you’ll notice, we have come along pretty much on the level.  This tunnel wasn’t dug in the side of a hill.  It went into the ground slanting, and at such a gradual slope that the top can’t be very far under the surface.”

“What does that mean?” asked Charlie.

“It means that we haven’t much dirt over our heads, and if a bomb were to drop directly above us we’d be in a bad way.  I think we’d better keep on until we get to a deeper part of the cave, or whatever it is.”

“But we’ll have to go on in the dark,” objected Joe.  “There are only three more lights, and——­”

Suddenly came a muffled explosion, and the lights went out, leaving the place in black gloom.

“Now there aren’t any lights,” said Charlie, when the echo of the dull roar had passed away.  The tunnel had been shaken, and there was a pattering sound all about the boys, as if little particles of earth had been dislodged, but no other damage appeared to have been done.

“It is dark!” said Blake.  “But come on.  Use your pocket lights.  No, hold on.  We’ll use only one at a time.  No telling how long we may need them.”

Bringing out his own light, he flashed it on and led the way.  Above them a continuous roar could now be heard, and they guessed that the airships were attacking in force, directly over the German camp, and were being fired at from all sides.

“One bomb must have splattered Fritz’s electric plant,” observed Joe, as he and his chums hurried on as best they could in the somewhat dim light of the little pocket lamp Blake carried.

Hardly had he spoken when there came a tremendous explosion—­one that staggered the boys and seemed to crumple up the tunnel as though it were made of paper.

They had no time to cry out.  They were thrown down and felt rocks and stones falling about them, while their ears were deafened by the roaring sound.

Then came silence and darkness—­a darkness that weighed heavily on them all, while Blake, who had been in the lead, tried to move his hand to flash on the electric light that had gone out or been broken.  He could barely move, and as he felt dirt and rocks all about him there was borne to his senses the horrible message: 

“Buried alive!”

After that thought mercifully came unconsciousness.

CHAPTER XXV

THE END OF LABENSTEIN

How long they lay entombed in the German tunnel the moving picture boys did not know.  They must have been unconscious for some time.

Joe was the first to regain his senses.  Telling about it later, he said he dreamed that he had been taking views in Earthquake Land and that, somehow or other, a volcano had fallen on his chest.  He had difficulty in breathing, and no wonder, for as he came to his senses he found that a great rock and a pile of earth were across him.