was no sound of lowing cows or snorting steers,
and there came to the ears of Nort and Dick no distant shouts of Bud
and the cowboys, though the main herd, with the men in charge, could
not have been more than two miles away. But, for all that, our heroes
were as completely isolated as though a hundred miles distant from
civilization.

"I can't understand it!" murmured Dick.

"Nor I," said Nort, "It's just as if those cattle had dropped out of
sight in a hole in the ground. Maybe they did, Dick."

"What do you mean?" asked his brother.

"I mean maybe those mysterious professors have been digging big mining
holes around here, and that bunch of steers we were chasing just
naturally slipped into one. We'd better look out, or we'll drop out of
sight ourselves!"

Though he spoke half jokingly, there was some seriousness in Nort's
voice, and Dick realized it.

"Those professors sure are queer, with their digging operations," Dick
agreed. "I'd like to know what they are after, and why they're hanging
around Diamond X."

"Well, I'd like to know that, too," said Nort, "but first of all I'd
like to know our way out of this place. There must be some way out, as
we didn't have any trouble finding a way in."

"Of course we can get out," Dick answered. "There aren't any trees to
amount to anything, and we aren't fenced in. We can ride in any
direction we like, and I say let's ride somewhere."

"I'm with you," spoke his brother. "But the only trouble is we might
be riding farther and farther away from Bud and the rest of the
fellows. Why not try to locate that bunch of cattle we're after?
They'll be heading directly away from the main herd, I take it, and if
we locate them all we'll have to do will be to drive them right about
face, and we'll get back where we belong."

"All right, let's find the steers," assented Dick.

They started their ponies, which, doubtless, had been glad of the
little breathing spell. But it was one thing to say find the missing
steers, and another to do it. One swale seemed to so melt in with an
adjoining one, and one hill to merge with its mate, that they all
looked alike to the boys, who, as it developed afterward, kept working
their way farther and farther off from their friends.

"Hang those steers! Where are they, anyhow?" exclaimed Nort after half
an hour of search, during which no signs had been seen.

"Let's try over this way," suggested Dick, turning to the left.

Thoug