"What has happened? What caused it?" cried Mark, as he crawled over to
where Jack sat on the ceiling, with a dazed look on his face.

"I don't know. Something went wrong. Here comes Professor Henderson and
Mr. Roumann. We'll ask them."

The two scientists were observed approaching from the pilot-house. They
walked along what had been the ceiling, and when they came to the
engine room they had to climb over the top part of the door frame.

"What's wrong?" asked Jack.

"Our center of gravity has become displaced," answered Mr. Henderson.
"The gravity machine has either broken, or some one has been tampering
with it. Did either of you boys touch it?"

"No, indeed!" cried Mark, and his chum echoed his words.

"I wonder if Washington could have meddled with it?" went on the
scientist.

At that moment the colored cook came along, making his way cautiously
into the engine room. He was an odd sight. Bits of carrots, turnips and
potatoes were in his hair, while from one ear dangled a bunch of
macaroni, and his clothes were dripping wet.

"My kitchen done turned upside down on me!" wailed Washington, "an' a
whole kettle ob soup emptied on my head! Oh, golly! What happened?"

The aged scientist looked toward the German. The latter was gazing up