mass. Just see how the
whole story is revealed right there in this gorge! You can see the
streaks of basalt, which we know lie in horizontal layers, and rest on
vertical strata of the Carboniferous and Triassic age."

"Whoa--there!" groaned Long Lester. "Would you mind telling us that
again, in words of one syllable? I calc'late it must be a mighty
interesting yarn, from the hints you've let out now and ag'in, but how'n
tarnation----"

"Yes," grinned Ted, "do tell it, Mr. Norris, so's Les and I can get it
too."

"'Bout all I've got any strangle hold on," complained the old man, "so
fur, is thet these yere valleys was gouged out by the glaciers, a good
long spell ago. Now there's one thing I'm a-goin' to ask you, Mister,
before we go any further. What did you mean by that there--coal age?"

"That," vouched Norris, "was when most of the coal was formed, away back
before man appeared on earth,--before there were any of the plants and
animals as we know them to-day.

"Picture a time when the water was covered with green scum, and the air
was steamy, when the swampy forests were composed of giant ferns and club
mosses and inhabited by giant newts and salamanders, dragon-flies and
snakes."

"How--how do you know all thet?" gasped Long Lester.

"Partly by the fossils. It's a big study,--geology, we call it,--and the
scientists who reason these things out use what has been discovered by
astronomy and chemistry and a lot of other sciences. It's a long story."

"But a _thriller_," Ace assured them, as Norris lighted his pipe on the
lee of a bowlder. "Can't we rest here a few minutes, Mr. Norris? Those
burros were about winded. Can't get 'em to budge yet. Come on, fellows,
snuggle up," as Norris seated himself compliantly, back against the
bowlder. They all crept close, for the wind was blowing hard.

"Where did this earth come from in the first place?" asked Ted.

"Well, of course you know that our sun is only one of millions of stars,
and very far from being the largest, at that. Some larger star, in
passing the sun, by the pull of its own greater gravity, separated some
large fragments from that fiery, gaseous mass, and started our planetary
system. We don't want to go too far into astronomy."

"But astronomy shows you how they know all this," Ace assured the old
man, who appeared divided between wide-eyed amazement and incredulity,
(as, indeed, were Ted and Pedro).

"Our earth, like the other planets, was one of