of more than 30,000 objects. Every
day adds to the discoveries as excavations are made, houses built, and
cuts made for railroads.

These objects are not found on the surface of the ground, but
ordinarily buried deeply where the earth has not been disturbed. They
are recovered from a stratum of gravel or clay which has been
deposited gradually and has fixed them in place safe from the air, a
sure proof that they have been there for a long time.

=Prehistoric Science.=--Scholars have examined the debris and have
asked themselves what men have left them. From their skeletons, they
have tried to construct their physical appearance; from their tools,
the kind of life they led. They have determined that these instruments
resemble those used by certain savages today. The study of all these
objects constitutes a new science, Prehistoric Archaeology.[1]

=The Four Ages.=--Prehistoric remains come down to us from very
diverse races of men; they have been deposited in the soil at widely
different epochs since the time when the mammoth lived in western
Europe, a sort of gigantic elephant with woolly hide and curved tusks.
This long lapse of time may be divided into four periods, called Ages:

1. The Rough Stone Age.

2. The Polished Stone Age.

3. The Bronze Age.

4. The Iron Age.

The periods take their names from the materials used in the
manufacture of the tools,--stone, bronze, iron. These epochs, however,
are of very unequal length. It may be that the Rough Stone Age was ten
times as long as the Age of Iron.

THE ROUGH STONE AGE

=Gravel Debris.=--The oldest remains of the Stone Age have been found
in the gravels. A French scholar found between 1841 and 1853, in the
valley of the Somme, certain sharp instruments made of flint. They
were buried to a depth of six metres in gravel under three layers of
clay, gravel, and marl which had never been broken up. In the same
place they discovered bones of cattle, deer, and elephants. For a long
time people made light of this discovery. They said that the chipping
of the flints was due to chance. At last, in 1860, several scholars
came to study the remains in the valley of the Somme and recognized
that the flints had certainly been cut by men. Since then there have
been found more than 5,000 similar flints in strata of the same order
either in the valley of the Seine or in England, and some of them by
the side of human bones. There is no longer any doubt that men