Among other things he did when he had his craft, was to aid a Miss Mary Nestor, who, in her cousin's small boat, the Dot, was having trouble with the engine, and you shall hear more of Miss Nestor presently, for she and Tom became quite friendly. Events so shaped themselves that Andy Foger was glad to loan Tom the Red Streak in which to search for the stolen Arrow, and it was in the later craft that Tom, his father and Ned Newton had a most thrilling adventure.
They were on their way down the lake when, in the air overhead they saw a balloon on fire, with a man clinging to the trapeze. They managed to save the fellow's life, after a strenuous endeavor. The balloonist, John Sharp, was destined to play quite a part in Tom's life.
Mr. Sharp was more than an aeronaut—he was the inventor of an airship—that is, he had plans drawn for the more important parts, but he had struck a "snag of clouds," as he expressed it, and could not make the machine work. His falling in with Mr. Swift and his son seemed providential, for Tom and his father were at once interested in the project for navigating the upper air. They began a study of Mr. Sharp's plans, and the balloonist was now in a fair way to have the difficulty solved.
His airship was, primarily an aeroplane, but with a sustaining aluminum container, shaped like a cigar, and filled with a secret gas, made partly of hydrogen, being very light and powerful. It was testing the effect of this gas on a small model of the aluminum container that the explosion, told of in the first chapter, occurred. In fact it was only one of several explosions, but, as Tom said, all the while they were eliminating certain difficulties, until now the airship seemed almost a finished thing. But a few more details remained to be worked out, and Mr. Swift and his son felt that they could master these.
So it was with a feeling of no little elation, that the young inventor followed Mr. Sharp into the shop. The balloonist, it may be explained, had been invited to live with the Swifts pending the completion of the airship.
"Do you think we'll get on the right track if we put the needle valve in?" asked Tom, as he noted with satisfaction that the damage from the explosion was not great.
"I'm sure we will," answered the aeronaut. "Now let's make another model container, and try the gas again."
They set to work, with Mr. Swift helping them occasionally, and Garret Jackson, the engineer, lending a hand whenever he was needed. All that afternoon work on the airship progressed. The joint inventors of it wanted to be sure that the sustaining gas bag, or aluminum container, would do its work properly, as this would hold them in the air, and prevent accidents, in case of a stoppage of the engine or propellers.
The aeroplane part of the airship was all but finished, and the motor, a powerful machine, of new design, built by Mr. Swift, was ready to be installed.
All that afternoon Tom, his father and Mr. Sharp labored in the shop. As it grew dusk there sounded from the house the ringing of a bell.