The second cave, its entrance being almost at an angle of ninety degrees with the first, was tenanted. Both men recognized in the snub-nosed object projecting far above their heads the bow of a military Zeppelin.
Hamerton could have danced with sheer delight. He had discovered what was supposed to be the shell-proof lair of three powerful airships. Deep in the bowels of the earth they were immune from hostile shell. A high-angled fire might result in a projectile dropping into the vast circular pit, but the possibility of the aircraft being damaged by fragments of shells was guarded against by the provision of massive steel doors sliding on rollers.
Evidently the Zeppelins were being made ready for a flight, for the doors were wide open. In the third cavern lights burned at the farthermost end, and a party of officers and men were busily engaged in overhauling the after-car.
"Seen enough?" asked Detroit. "Let's quit."
"Suppose we must," replied Hamerton reluctantly. "It must be close on dawn, and we'll have to find a place to stow ourselves away."
"That airship facing the incline can come out of its dogbox all right, but I don't see how the others can be turned. There can't be more than a few feet between their extremities and the cliff when they are hauled out."
"Hardly. The faintest bump would do no end of damage."
"I wish the whole crowd of them would meet with no end of damage," said the Sub vengefully. "But come on, we mustn't hang about here till morning. I heard those fellows say that one of the airships was to be made ready by daybreak."
"One minute; I guess I'd like to look around over there," said Detroit, pointing to the centre of the circular bed of the pit. So saying, he made his way cautiously from the shelter of the cliff, and Hamerton, guessing that his comrade was on the verge of a new discovery, followed.
For the first ten yards the floor was literally covered with a network of tram lines. There were treble parallel tracks, points, and sidings galore. It reminded the Sub of a miniature Clapham junction.
"I thought so," he announced. "We've hit the edge of a gigantic turntable. This is how they slew round their blessed Zeppelins."
The floor of the turntable was almost as smooth and level as a billiard table. There was not a single projection that would form the slightest hindrance to its intended burden. Almost in the centre were a couple of flat trapdoors for the purpose of gaining access to the machinery underneath, but the actual moving of the turntable was controlled by means of electric switches from a cabin close to the wall of the basin.