'The physical description
of the world' presents a picture of all that exists in space -- of the
siimultaneous action of
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natural forces, together with the phenomena which they produce.
But if we would correctly comprehend nature, we must not entirely or
absolutely separate the consideration of the present state of things from
that of the successive phases through which they have passed. We can not
form a just conception of their nature without looking back on the mode of
their formation. It is not organic matter alone that is continually
undergoing change, and being dissolved to form new combinations. The globe
itself reveals at every phase of its existence the mystery of its former
conditions.
We can not survey the crust of our planet without recognizing the traces of
the prior existence and destruction of an organic world. The sedimentary
rocks present a succession of organic forms, associated in groups, which
have successively displaced and succeeded each other. The different
super-imposed strata thus display to us the faunas and floras of different
epochs. In this sense the description of nature is intimately connected
with its history; and the geologist, who is guided by the connection
existing among the facts observed, can not form a conception of the present
without pursuing, through countless ages, the history of the past.
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