st
through which it would have been utterly impossible to have seen anything
a hundred feet away.

Tom for one did not like the coming of that fog just when they were about
to drew near the land of their hopes. Unlike a vessel, they could not
come to anchor and ride it out, waiting for the fog to lift; but must
drive on, and desperately strive to find some sort of landing.

"The thickest fog I ever saw!" Jack observed, after they had been passing
through the moist gray blanket of mist for some little time.

"Just the usual kind you'll meet with on the sea at times," answered the
lieutenant. "I was caught in one when out on the fishing banks, and it
wasn't any too pleasant a feeling it gave me either. But for our compass
we'd never have reached shore again."

"And but for the compass right now," said Tom, "it would be next to
impossible to steer a straight course."

"One good thing," Jack told them; "very little danger of a collision,
such as vessels are likely to encounter in so dense a fog."

"No, the air passage across the Atlantic hasn't become so popular yet
that we have to keep blowing a fog horn while sailing," laughed Colin.

All of them were feeling considerably brighter, now that their wonderful
venture seemed to be drawing close to a successful termination. If only
their luck held good and allowed them to make a safe landing, they felt
they would have good reason for gratitude.

"What makes it feel so queer at times?" Jack asked later on. "Why, I seem
to have the blood going to my head, just as happened when looping the
loop, and hanging too long in stays."

"I've noticed the same thing myself," added Colin briskly, "and tried to
figure out the cause. Tom, what do you say about it?"

"A queer situation has arisen, according to my calculation," the pilot
told them. "Fact is, without being able to see a solitary thing anywhere
about us, above or below, it's often impossible to know when we're
sailing on a level keel, or flying upside down!"

"That's a fact," admitted Lieutenant Beverly. "When you haven't the
slightest thing to guide you, stars, sun, or earth, how can you tell
which is up or which is down? We go forward because of the compass; but
part of the time I do believe, just as you say, Tom, we've been flying
upside-down!"

"I don't fancy this way of flying," Tom announced. "I think it would be
better for us to climb in order to see if we can get out of this
pea-soup."

"Ditto here!" echoe