best begin. I suppose by going back to first principles, and
after determining what makes an aeroplane engine noisy, try to
figure out how to make it quiet. Now as to the first, the
principle causes of noise are--"

And at that instant there broke on Tom's ears a succession of
discordant sounds which seemed to be a combination of an Indian's
war whoop and a college student's yells at a football game.

"Now I wonder what that is!" mused the young inventor as he
hastily arose. "Better solve that problem before I tackle the
aeroplane motor."



CHAPTER VIII
THROUGH THE ROOF



Tom rushed from his private office, and when he reached the
outer door he heard with more distinctness the sounds that had
alarmed him. They seemed to come from a small building given over
to electrical apparatus, and which, at the time, was not supposed
to be in use. It had been Tom's workroom, so to speak, when he
was developing his electric runabout and rifle, but of late he
had not spent much time in it.

"Somebody's in there !" reflected the young inventor, as he
heard yells coming from the open door of the place. "And if it