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