overy.

Nothing was said to the Professor about the visit to the cave. It must
be confessed that they felt a little sheepish about this, as such a
thing as deceiving the Professor was farthest from their thoughts, but
there was no concerted agreement to keep him in the dark. Either would
have scorned to enter into such an agreement.

The boys were more than surprised that evening when the Professor
brought out some of the treasures he had brought from the cave and
exhibited them. Among them was a crude implement of stone, which had the
appearance of a cutting instrument. Another was a small stone vessel,
unmistakably showing human manufacture.

The sight of these did not, at first, interest the boys, but when the
Professor stated that the cave was undoubtedly of very ancient origin,
George could not resist the inevitable question, "How can that be
determined?"

"In the study of paleontology an effort has been made to classify the
different periods of man's life on the planet, so that we have the stone
age, which is the earliest, the bronze age, and the age of iron."

"How far back in the history of the world has evidence been found of the
existence of man?"

"In the chalk cliffs of England, and also in like formations in Germany,
skulls have been found which indicate an existence back to a period
fully 500,000 years ago."

"What reason is there to assume that if they were found in those chalk
deposits, that they must have been that far back?"

"Because it was fully that long ago in the period of the world formation
when the chalk beds were made, and this seems to be conclusive evidence
of great antiquity."

"Is it not singular that more evidence of that condition is not found
than the recovery of a few bones?"

"Not when it is considered that the earth is constantly undergoing
change, first in one place and then in another. Have you ever heard of
the great continent, which was supposed to be lost in mid-Atlantic,
called Atlantis? Plato refers to it, and attributes the first knowledge
of it as coming from Solon, who visited Egypt and there learned from the
wise men that a great country, to the west of the Pillars of Hercules,
which Gibraltar was called in ancient times, had disappeared thousands
of years before; and they further informed the great Grecian lawgiver
that the earth had been peopled and repeopled many times before in ages
past."

"Why was it necessary to repeople the earth? Were they all destro