e that enable an anthropologist to
make rough estimates as to the relative lengths of the different periods
into which prehistoric time is divided. Gabriel de Mortillet, one of the
most industrious students of prehistoric archaeology, ventured to give
a tentative estimate as to the numbers of years involved in each
period. He of course claimed for this nothing more than the value of a
scientific guess. It is, however, a guess based on a very careful study
of all data at present available. Mortillet divides the prehistoric
period, as a whole, into four epochs. The first of these is the
preglacial, which he estimates as comprising seventy-eight thousand
years; the second is the glacial, covering one hundred thousand years;
then follows what he terms the Solutreen, which numbers eleven thousand
years; and, finally, the Magdalenien, comprising thirty-three thousand
years. This gives, for the prehistoric period proper, a term of about
two hundred and twenty-two thousand years. Add to this perhaps twelve
thousand years ushering in the civilization of Egypt, and the six
thousand years of stable, sure chronology of the historical period, and
we have something like two hundred and thirty thousand or two hundred
and forty thousand years as the age of man.

"These figures," says Mortillet, "are certainly not exaggerated. It is
even probable that they are below the truth. Constantly new discoveries
are being made that tend to remove farther back the date of man's
appearance." We see, then, according to this estimate, that about a
quarter of a million years have elapsed since man evolved to a state
that could properly be called human. This guess is as good as another,
and it may advantageously be kept in mind, as it will enable us all
along to understand better than we might otherwise be able to do the
tremendous force of certain prejudices and preconceptions which recent
man inherited from his prehistoric ancestor. Ideas which had passed
current as unquestioned truths for one hundred thousand years or so are
not easily cast aside.

In going back, in imagination, to the beginning of the prehistoric
period, we must of course reflect, in accordance with modern ideas on
the subject, that there was no year, no millennium even, when it could
be said expressly: "This being was hitherto a primate, he is now a man."
The transition period must have been enormously long, and the changes
from generation to generation, even from century to cen