logists
can just about piece together the history of the earth from the fossils
that have been found, but no one locality gives it all. They have
found part of the story in America and part in Africa, and parts
in Europe and Asia. And from that series of fossils--and some other
evidence--scientists have about agreed that since the earth was formed,
about twenty whole mountain ranges, one after another, must have been
formed and worn away almost to sea level."

"How do they make that out?" Ted looked skeptical.

"That's another long story. I'm no professor. But----"

"You can't prove it."

"Neither can you disprove it, any more than you can the conclusions on
which astronomy, higher mathematics, any of the sciences--are based."

"I suppose so! Gee, I'd like to study those things for myself!" sighed
Ted, seating himself beside the others on a dry ledge while they ate
their sandwiches.

"Find a valuable fossil and you've earned a college education," Ace
challenged him. "And you know, fossils are not necessarily fish or
insects or skeletons or tree trunks that have been turned to stone."

"To stone?"

"By the removal of their own tissues and replacement by mineral matter. A
fossil may be merely the print of a leaf of some prehistoric plant on
sandstone, or the footprint of some antediluvian reptile. In the National
Museum they have a cast of a prehistoric shad that shows the imprint of
every bone and fin ray."

"How on earth could that have been formed?" marveled Ted.

"Why, it was simply buried in fine mud, which first protects it from the
air, (and consequent immediate decay), then gradually fills every pore of
every bone, till by the time the mud has turned to stone, the bones are
ossified. Of course the animal matter has all dissolved away by this
time. Now if this mud that filled the pores happened to be silica, (a
sandy formation), it is possible to eat the surrounding limestone away
with acids and uncover the silica formation, see, old kid?"

"Aw, that stuff makes my head ache," protested Tim. "If I see any
ossified bones lying around, or even a footprint or leaf print in the
stone, I'll know I've found a fossil. But I thought we were chasing
fire-bugs."

"The impatience of youth!" Ace playfully squelched him, from the vantage
point of his slight seniority.

"What does the Bible say," laughed the Ranger, "about truth from the
mouths of babes?" And he arose a bit stiffly,--for he had had a strenuous
t