When Jack returned, rather breathless from lugging a load that a weaker man could not have managed, they carefully wrapped the battery box in an oilcloth tarpaulin, to prevent any damage to it from the dampness of the ground, then buried it with only the wires protruding, and with still a layer of two inches of dirt to be put on after a single small cable of many insulated strands had been attached.
Fred then took a length of heavy ordinary hemp rope, a little longer than sufficient to reach from one of the bracing wires to the ground. From this bracing wire he directly and indirectly connected up every metallic part of the aeroplane, except the engine.
He then heated a small straight iron rod almost white hot, and, with a bucket of water close at hand, forced the hot rod through the center of the strand of rope, immediately dropping the latter into the bucket to prevent it from burning through.
By this time his scheme was becoming apparent. He ran the cable of wire through the rope, attached one end to the batteries, then completed their concealment and finally hung the strand of rope over the fusilage of the plane as though it had been carelessly tossed there, but with a complete connection established.
No one, without picking the rope up for careful examination, could possibly have detected or even suspected its purpose. It just looked as though it had been left there for no particular purpose whatever.
Fred then went to the engine, did a few secret tricks that he knew of there, and then turned on the battery switch of the plane.
"Now," he said, "I think the trap's all set for our friend, the enemy. Let us hope he walks into it."
He gathered up all the tools and implements with which he had been working, carefully replaced them where they belonged, with his own hands again smoothed off the ground where the auxiliary battery box had been buried, and then, with a final survey of his surroundings and a gentle pat or two to the rope, pronounced their work completed.
"Let's go eat," said Big Jack. They started for the hangar, but had gotten but a few feet away when he halted.