rendezvous, somewhere back in this lot!"
declared Tom, as they hurried on. "I think we're on the track of a
mystery."

"Unless it turns out that some farmer has treated himself to an auto
with new tires of square tread, and is hauling wood," said Jackson. "It
may turn out that way."

"Yes, it may," agreed Tom. "But, taking everything into consideration,
I think we're on the verge of finding out something. Even if we do
discover that the owner of this auto is only hauling wood, he may be
able to help us to a clew as to the whereabouts of Mr. Nestor."

"How?"

"Well, maybe he was in his machine on the moor the night the call for
help came. He may even have aided to carry Mr. Nestor away. And if he
doesn't know a thing about it--which, of course, is possible--the man
who bought these queer tires can tell us who makes them, or who deals
in them, and we can find out what autoists around here have their cars
equipped with this odd tread."

"Yes," agreed Jackson, "that can be done."

And so they kept on, scouting here and there to either side of the
half-defined path, until they were far back from the spot where they
had left the Air Scout.

"We don't appear to be getting any warmer, as the children say,"
remarked Jackson, as he straightened up and looked about, for his back
ached from so much stooping over to look for the odd marks.

"We haven't seen anything yet, I'll admit," said Tom. "But it won't be
dark for another hour or so, and I vote that we keep on."

"Oh, I wasn't thinking of giving up!" exclaimed Jackson. "If there's
anything here--at the end of the route, as you might say--we'll find
it. Only I hope it doesn't turn out to be just a wood pile, from which
some farmer has been hauling logs."

"That would be a disappointment," assented Tom.

The day was waning, and they realized that they ought not to spend too
much time on what might turn out to be a wild goose chase. They were in
a lonely neighborhood, and while they were not at all apprehensive of
danger, they felt it would be best to get to shelter before dark.

"We'll want to send word to Mr. Swift that we're all right."

"Yes," said Tom, "I'd like to get to a place where I can telephone to
him or Mrs. Baggert. Well, if we don't find something pretty soon we'll
have to turn back. I must complete work on the new motor, for if I'm to
offer it to Uncle Sam for air scout purposes, the sooner I can do so
the better. Things are getting pretty hot over