"Well, maybe it's a good plan," agreed Tom.
"Of course," began Tom, "it would be"
He was interrupted by a shout from Koku, who had gone to the motor room, for the giant was as fascinated over machinery as a child. As he yelled there came a grinding, pounding noise, and the big ship seemed to waver, to quiver in the void, and to settle toward the earth.
"Something's happened!" cried Ned, as he sprang for the place where most of the mechanism was housed.
"Bless my toy balloon!" shouted Mr. Damon. "We're falling, Tom!"
It needed but a glance at the needle of the barograph to show this. Tom followed Ned at top speed, but ere either of them reached the engine room the pounding and grinding noises ceased, the airship began to mount upward again, and it seemed that the danger had passed.
"What can have happened?" gasped Tom.
"Come on, we'll soon see," said Ned, and they rushed on, followed by Mr. Damon, who was blessing things in a whisper.
The chums saw a moment later—saw a strange sight—for there was Koku, the giant, kneeling down on the floor of the motor room, with his big hands clasped over one of the braces of the bed-plate of the great air pump, which cooled the
