All that remained to do then, was to inflate the great gas bag. The adjustment of this to the frame proved tedious work. But at last it was done, and the folds all carefully straightened out, in itself an arduous job. The whole party was pretty well tired out by this time, and work was discontinued for the day.
“In the morning,” said the professor, “we will inflate the bag, and then there will be nothing more to detain us.”
The boys gave a cheer. It seemed almost too good to be true—the idea that before many hours had passed they would be flying high above old Mother Earth in a cloud cruiser, that for completeness and effectiveness surpassed their wildest dreams.
Between four and five o’clock the next morning the lads were astir. After early coffee and some fruit and rolls, the task of inflating the great bag was begun. Huge wooden tanks full of iron filings and metal scrap had already been erected. Acid was now added to the filings and the tops clamped on. Then the inflation pipes, purifier and nozzles were adjusted.
A cheer broke from the boys as they saw the huge bag begin to swell like a live thing as the gas poured into it. By noon the professor announced the inflation as being sufficient. At that time, the great yellow bag was as tight as a drum almost, and the heat of the sun served to swell it still further. While the bag had been filling, the under frame of the dirigible had been weighted down by bags of sand. Otherwise it would have risen of its own volition.
The last things loaded on the framework were several cylinders of hydrogen gas at tremendous pressure. This was the reserve supply of the adventurers, and the tanks contained enough almost to refill the bag in case of necessity. A hasty lunch was consumed at the consul’s table, and Nat gave final instructions to the man who had been employed to take care of the Nomad during their absence.
This done, there was nothing else to wait for, and at one-thirty sharp, the professor gave a final look over things. Then he turned to Ding-dong Bell.
“You can take your place at the motor,” he said. “Mr. Tubbs, you will attend to the handling of the craft as we rise.”
The versatile Mr. Tubbs, whose moving picture apparatus was in readiness, paused to take a few pictures, and then mounted to his place in the pilot-house.
Nat and his chums bade good-bye to the consul, and then took their places. It was Nat and Joe’s task to attend to the throwing off of ballast as they arose.