slept well on board the _Annihilator_, which was speeding so swiftly
through space--slept as comfortably as they had on earth. Each hour
brought them nearer the moon, and they figured on landing on the
surface of that wonderful and weird body in about three days more.

It was on the morning of the fourth day when, as Mark and Jack were
taking their shift in the engine room, that Jack happened to glance
from the side observation window, which was near the Cardite motor.
What he saw caused him to cry out in surprise.

"I say, Mark, look here! There's the moon over there. We're not heading
for it at all!"

"By Jove! You're right!" agreed his chum. "We're off our course!"

"We must tell Professor Henderson!" cried Jack. "I'll do it. You stay
here and watch things."

A few seconds later a very much alarmed youth was rapidly talking to
the two scientists, who were in the pilot-house.

"Some unknown force must have pulled us off our course," Jack was
saying. "The moon is away off to one side of us."

To his surprise, instead of being alarmed, Mr. Roumann only smiled.

"It's true," insisted Jack.

"Of course, it is," agreed Mr. Henderson. "We can see it from here,
Jack," and he pointed to the observation window, from which could be