aboard, as they probably will have, we'll--"

"Bless my armor plate!" interrupted Mr. Damon. "Please don't talk
about such hair-raising things, Ned! Talk about something pleasant."

"All right," agreed Tom's chum, and then, as the airship sailed
along, high above the earth, they talked of many things.

"I think when we sight Logansville." said Tom, after a while, "that
I will come down in some quiet spot, before we reach the city."

"Don't you want to get into a crowd?" asked Ned.

"No, it isn't that. But Mr. Foger lives there you know, and, though
he may not be at home, there are probably some men who are
interested in the thing he is working at."

"You mean smuggling?"

"Well, I wouldn't say that. At the same time it may have leaked out
that we are after the smugglers in an airship and it may be that Mr.
Whitford doesn't want the Fogers to know I'm on the ground until he
has a chance to work up his clew. So I'll just go slowly, and remain
in the background for a while."

"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 cylinders of the motor. The pump
had torn partly away from its fastenings. Kneeling there, pressing
down on the bed-plate with all his might, Koku was in grave danger,
for the rod of the pump, plunging up and down, was within a fraction
of an inch of his head