passageway that
led to the grotto of brown cauliflower-like encrustations. But here, when
they found that the left-hand passageway meant going on hands and knees,
they chose the other turn. (They came that near to catching up with the
fugitives!)

With the suddenness of events in a dream, they came into a vast chamber
that at first glimpse, lighted as it was by the carbide lamp, gave the
impression of a baronial ruin. The boys whistled simultaneously under
their breath. At the far end stood a huge stone elephant,--or so it
appeared at the first startled glance,--and beside him a gnome and
several weird beasts vaguely reminiscent of the monsters of prehistoric
times.

When Ted could speak, he whispered, "What are they? Fossils?"

Ace laughed. "I should say not. They're nothing but dripstone, can't you
see?--They'd be 'some fossils'! Why, if we could find just one fossil as
big as that, our fortunes would be made--absolutely."

"Gee! Then I'm sure going to keep my eyes peeled."

"I thought," put in Radcliffe, "that fossils were little stone worms.
I've found those aplenty."

"Fossils," explained Ace, (fresh from first-year geology), "are any
remains of plants or animals that lived, either on land or in the sea, in
ancient times. A lot of those we find to-day were shell-fish and other
marine life."

"Gee!" grinned Ted, "doesn't he talk like a professor? I'm going to call
you professor after this, old Scout!"

"Go on," the Ranger urged, ignoring this sally, "I'm interested."

"So am I, honestly," amended Ted contritely.

"There were land animals, too, that got buried in the accumulating
sediments and fossilized. Times when the ocean over-ran the land, they
got drifted into it, and sank, and got buried under the sands that made
our sandstones----"

"This floor is sandstone!" interpolated Ted.

"Yes. Or they got buried in the ground-up shells that made our
limestone,--like the walls of the cave,--or some of them were buried in
mud."

"I suppose," offered Ted facetiously, "that the mud made mudstones," and
he laughed till his voice echoed and reechoed startlingly.

"Ha, ha! You're right!" Ace turned the laugh on him. "Go to the head of
the class. I'll show you mudstone when we come to it."

"Why, then," ventured the Ranger, "this must be a topping place to find
fossils."

"Provided," Ace admitted, "the cave is not of too recent formation. But
as I was about to say," (seeing their undoubted interest), "geo