Frank had picked up the padlock belonging to the doors, and which was hanging, open, on a convenient nail. He knew that just outside there was a long and stout chain, which had been used somehow with the lumber brought from the yard, and forgotten when the wagon pulled out.
It was in connection with that same chain that his thoughts ran just now. And he had faith to believe that, if given just half a minute of time, he could fix it so that the bold thieves would find some difficulty in breaking away from old Mother Earth when Jules chose to set that propeller whizzing.
Again was Frank indebted to the noise of the churning engine, for it effectually deadened what clanking sounds the chain made when he took hold of its ends, and crept forward.
He kept as low down as he could. Even the moon seemed to be in full sympathy with the boy’s mission. She had very conveniently hidden her smiling disc behind quite a dark cloud just then, and brought a shadow across the face of the land. Perhaps Jules had noticed this fact. Perhaps he was waiting until it grew light again, so he could see what lay ahead of them. This ascending from an unknown field must have all sorts of dangers attached to it, which an experienced aviator understood.
And so Frank was allowed to reach the rear of the aeroplane without being detected. His perfect knowledge concerning the build of the machine served him well at this crisis, for he knew just where to go in order to find what he sought.
Fortune favored him to a most remarkable degree. Why, if he had the ordering of the whole affair he could hardly have improved upon the arrangements. They had pushed the aeroplane out possibly a score of feet beyond the doors of the hangar. And in so doing the wheels just avoided a weighty object which Frank had had dumped there, intending to use the same as an anchor, to which the monoplane could be fastened when they came to trying her propeller at full speed.
This was a large iron post, that must have weighed all of three hundred pounds. It had a large ring attached. Once upon a time it stood in front of the Whympers domicile, and horses were tied to the ring; but lately it had come to be a nuisance, so that the colonel had ordered it uprooted, and taken to the dump in the rear, from which the young aviators had rescued it.
And through that same ring Frank now slipped his chain. His purpose was plain. Instead of keeping restive horses from taking to their heels, the old post was now intended to act as a restraining power to a steed of the upper air currents, and curb the ambition of the monoplane when the propeller started to turning.
When Frank had managed to pass his chain through the frame of the rudder he brought the two ends together, and snapped the padlock shut. Its jaws held the ends of the chain fast, forming an effectual brake.
Satisfied that he had managed to anchor the aeroplane to the ground, the boy next crept back toward the shed. He knew that the explosion must come in a brief time now, and wished to be as far away from the two robbers at that critical moment as possible.