5,400,000 "
Ordovician 5,400,000 "
Cambrian 8,000,000 "

Archaean Keweenawan Unknown (probably
Animikie at least
Huronian 50,000,000 years)
Keewatin
Laurentian

CHAPTER V. THE BEGINNING OF LIFE

There is, perhaps, no other chapter in the chronicle of the earth that
we approach with so lively an interest as the chapter which should
record the first appearance of life. Unfortunately, as far as the
authentic memorials of the past go, no other chapter is so impenetrably
obscure as this. The reason is simple. It is a familiar saying that life
has written its own record, the long-drawn record of its dynasties and
its deaths, in the rocks. But there were millions of years during which
life had not yet learned to write its record, and further millions of
years the record of which has been irremediably destroyed. The first
volume of the geological chronicle of the earth is the mass of the
Archaean (or "primitive") rocks. What the actual magnitude of that
volume, and the span of time it covers, may be, no geologist can say.
The Archaean rocks still solidly underlie the lowest depth he has ever
reached. It is computed, however, that these rocks, as far as they are
known to us, have a total depth of nearly ten miles, and seem therefore
to represent at least half the story of the earth from the time when it
rounded into a globe, or cooled sufficiently to endure the presence of
oceans.

Yet all that we read of the earth's story during those many millions of
years could be told in a page or two. That section of geology is still
in its infancy, it is true. A day may come when science will decipher a
long and instructive narrative in the masses of quartz and gneiss, and
the layers of various kinds, which it calls the Archaean rocks. But we
may say with confidence that it will not discover in them more than
a few stray syllables of the earlier part, and none whatever of the
earliest part, of the epic of living nature. A few fossilised remains of
somewhat advanced organisms, such as shell-fish and worms, are found
in the higher and later rocks of the series, and more of the same
comparatively high types will probably appear. In the earlier strata,
representing an earlier stage of life, we find only thick seams of black