stone, bronze, and iron. But all countries have not lived in the same
age at the same time. Iron was employed by the Egyptians while yet the
Greeks were in their bronze age and the barbarians of Denmark were
using stone. The conclusion of the polished stone age in America came
only with the arrival of Europeans. In our own time the savages of
Australia are still in the rough stone age. In their settlements may
be found only implements of bone and stone similar to those used by
the cave-men. The four ages, therefore, do not mark periods in the
life of humanity, but only epochs in the civilization of each country.

=Uncertainties.=--Prehistoric archæology is yet a very young science.
We have learned something of primitive men through certain remains
preserved and discovered by chance. A recent accident, a trench, a
landslip, a drought may effect a new discovery any day. Who knows what
is still under ground? The finds are already innumerable. But these
rarely tell us what we wish to know. How long was each of the four
ages? When did each begin and end in the various parts of the world?
Who planned the caverns, the lake villages, the mounds, the dolmens?
When a country passes from polished stone to bronze, is it the same
people changing implements, or is it a new people come on the scene?
When one thinks one has found the solution, a new discovery often
confounds the archæologists. It was thought that the Celts originated
the dolmens, but these have been found in sections which could never
have been traversed by Celts.

=What has been determined.=--Three conclusions, however, seem certain:

1.--Man has lived long on the earth, familiar as he was with the
mammoth and the cave-bear; he lived at least as early as the
geological period known as the Quaternary.