He pulled a lever toward him, turned a wheel and signalled to Washington to start the dynamo. There was a sound of buzzing machinery, which was followed by a hiss as the gas began to enter the cylinder under pressure. Would it stand the strain? That question was uppermost in every one’s mind save the professor’s. He only cared to see the cylinder leave the ground, carrying the weight with it. That would prove his long labors were crowned with success. Faster and faster whirred the dynamo. The gas was being generated from the air. The secret chemical made a hissing which could be heard for some distance. The gage registered a heavy pressure. Anxiously the professor watched the cylinder. “There!” he exclaimed at length. “It has all the gas it can hold. Now to see if it works!” He disconnected the pipe leading from the generator. This left the cylinder free. It seemed to tremble slightly. There appeared to be a movement to the hundred pound weight which rested on the ground. It was as if it was tugging to get loose. “There it goes! There it goes!” cried Mark, joyfully. “Hurrah!” shouted Jack. “There she rises!” “It suttinly am projectin’ itself skyward!” yelled Washington, coming from the dynamo. Sure enough the cylinder was slowly rising in the air, bearing the weight with it. It had lifted it clear from the ground and was approaching the roof of the big shed. “It will work! It will work!” exclaimed the professor, strangely excited. The next instant the cylinder, carrying the weight, sailed right out of an open skylight, and began drifting outside the shop, and across the fields. “Quick! We must get it back!” cried Mr. Henderson. “If it gets away my secret may be discovered and I will lose all! We must secure it!” But the cylinder was now two hundred feet in the air and being blown to the east, the weight dangling below it, making it look like a miniature airship. “We can never catch that!” cried Mark. CHAPTER III WASHINGTON DECIDES “We must catch that cylinder!” the professor exclaimed. “Some one may find it when it comes down and analyze the gas. Then he would discover how to make it. The cylinder must come down!” “Don’t see how we can proximate ourselves inter th’ vicinity of it lessen we delegate th’ imperial functions of ornithological specimens t’ some member of this here party,” observed Washington. “If you mean we can’t catch that there contraption unless we turn into birds I’ll show you that you’re mistaken!” cried Andy Sudds. “I guess I have a trick or two up my sleeve,” and the old hunter quickly threw open the breech of his gun and inserted a couple of cartridges.