nd in dry places possibly lichens
covering the rocks, were the highest forms of vegetable life. Animal
life, if present, for the fact is denied by some, occurs in the very
lowest form, merely structureless bodies, with no especial organs of
sense, or nutrition: and their motion consisting simply in protruding
and withdrawing hair-like processes.<4> Such was the beginning of life.
This vast period of time, which includes the beginning, is known among
geologists as Archean time.

From the close of this age, the history of life properly commences. It
might be well to explain the means which the geologist uses to interpret
the history of the globe. It is now understood that the forces of nature
have always produced the same results as they do now. From the very
earliest time to the present, rocks have been forming. There, where
conditions were favorable, great beds of limestone, formed from shells
and corals, ground up by the action of the sea<5>--in other places,
massive beds of sandstone or of sand, afterward consolidated into
sandstone--were depositing. On the land surface, in places, great beds
of vegetable _debris_ were being converted into coal. Now we can easily
see how the remains of organic bodies, growing at the time of the
formation of these beds, should be preserved in a fossil form. Limestone
rocks are thickly studded in places with all sorts of marine formations.
Coal fields reveal wonders of early vegetative growth. From sandstone
rocks, and shaly beds, we learn strange stories of animal life at the
time they were forming. From a careful study of these remains together
with the formation in which they occur, not only in one locality but all
over the earth, geologists have gradually unfolded the history of
life on the globe. It is admitted that, at best, our knowledge in that
direction is fragmentary. This arises from errors in observation as well
as that fossil formations are rare, or at least localities where they
are known to exist are but few. So our knowledge of the past is as if we
were examining some record from which pages, chapters, and even volumes,
have been extracted.

Illustration of Paleozoic Forest---------------

In consequence of this imperfect record we can not, as yet, trace a
gradual successive growth from the low forms of animal and plant, life,
that characterized the closing period of Archean time, to the highly
organized types of the present. The record suddenly ceases and when
we a