mountain
meadows.

For a day or two, all the boys could talk, think or dream about was the
adventures they had just been through. But at last they had relieved
their minds to some extent, and one evening around the fire, Norris gave
them his long promised explanation of some of the natural wonders they
had seen.

"I have already told you," began Norris, "how the earth probably
originated. That much the astronomer has given us. And before the
geologist can begin to interpret the evolution of our earth, he has to
know what scientists have established in the fields of chemistry,
mechanics and geodesy,--the study of the curvature and elevation of the
earth's surface. He then proceeds to theorize, hand in hand with the
paleontologist, or student of ancient life. The newest theory is in line
with what I learned in 1917 at Yale."

"It's all theory, then?" asked Ted.

"Just as all sciences are, to some extent. Did I tell you that when our
planetary system was disrupted from the sun, it was less than a hundredth
part of the parent body? And our earth is a good deal less than a
millionth of the size of our sun, and our sun is among the smaller of the
stars of the firmament."

"Phew!" whistled Long Lester, round eyed, while Ted and Pedro sat
motionless.

"Picture the earth and moon, revolving about the sun, gathering by force
of their own gravity-pull the tiny planetesimals nearest them, these
bodies hurling themselves into the earth mass at the rate of perhaps ten
miles a second!----"

"It shore must have het things up some," said Long Lester.

"It did! Literally melted the rocks. On top of that, this original earth
mass, composed of molten rock and gases and water vapor, was condensing.
Probably by the time it had engulfed all the stray planetesimals it
could, it was anywhere from 200 to 400 times as large as it is now. It
has been shrinking ever since."

"Is it still shrinking?" gasped the old prospector.

"Sure thing! But not so fast that you will ever know the difference in
_your_ lifetime. It only shrinks at times; then the earth's surface
wrinkles into mountain ranges."

"How many times has that been, sixteen?" suggested Ace.

"We'll come to that. As I was going to say, while the earth was so hot,
it kept boiling, as it were, inside, and the molten matter kept breaking
through the cold outer shell in volcanoes, as the heat rose to the
surface."

"Thet sure must have been hell," laughed the old man.

"As