f one single
group of these rocks, among many equally vast; when it was found that,
in the memory of man, during the lapse of at least five thousand years,
the earth had undergone no appreciable change; when it was found that
the earth was the result of the action of laws existent in matter,--an
upheaving, a washing away, a hardening, a disintegrating through a
period of time beyond the conception of man,--the theologians were
forced to substitute _periods_ for _days_. When the old walls which had
circumscribed man's mind became so crumbled as to allow of egress,
individuals broke through them and revelled in the freedom of
intelligent thought. When these walls were demolished by those who had
themselves erected them, they were leaped, in all directions, by ardent
explorers; and naturalists, no longer restrained by tradition, rushed
upon voyages of discovery into the teeming world before them.

For a while this emancipation exhausted itself in the contemplation of
the physical world, and an inquiry into brute life. Speculations and
theories might riot in a past which was a practical eternity. They had
unlimited space wherein to project, backward, the structure of the
universe. But this long-stretching past was to be peopled only by the
lower orders of animal life. The rocks were found to be filled with
stony remains of animals who perished when the sandstone, which built
old crumbling castles, was sea-shore mud; the chalk hills which bore
them were found to be made up of myriads of little creatures. These
humble representatives of life might be, must be, credited with a remote
antiquity. But man was not an animal. He was a being apart. Although he
was liable to heat and cold, disease and death, although his body was
made of the same materials as the brute's, and was subject to the same
laws of life, he was invested with an individuality which separated him
from them. For a while the old influence of theological rule held even
these venturous explorers to the ancient landmarks of human origin. By
and by, the same impulse which had before led men to examine the proofs
of physical creation induced them to consider the evidence of their own
advent upon earth. Certain Scriptural statements did not appear
reconcilable with each other. Cain went forth and builded a city; and
there were artificers in brass and iron. Now Cain was only one of two
men when he went forth. Whence came the citizens of that early
settlement, and how d