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.