476                                                 SILUEIA.                                       [Chap. XX.
 

CHAPTER XX.

OBJECTS   OF  THE  WORK.----GENERAL VIEW  OP   ANCIENT   LIFE FROM  ITS   EARLIEST   TRACES.—

PROGRESS  OF  CREATION, AFTER A LONG  INVERTEBRATE PERIOD, TO THE FIRST   PERIOD OF

FISHES, FOLLOWED BY THE EARLIEST EPOCHS OF LIZARDS AND MAMMALS.----GREAT FORMER

CHANGES OF THE SURFACE,   AS PROVED BY FRACTURES, DISLOCATIONS, AND   REVERSALS OF

STRATA.----SUCH GREAT MOVEMENTS INEXPLICABLE BY REFERENCE  TO MODERN  CAUSATION.

----GENERAL VIEW OF PALAEOZOIC SUCCESSION RESUMED.----CONCLUSION.

The main object of this work has now been accomphshed; for I have laid
before the reader a history of those types of former life which, by the
labours of geologists, have been found to occupy distinct stages in the
oldest deposits composing the crust of the earth. In aU this there is no
theory, but simply an accumulation of positive data. The order of such
successive generations is indeed much more clearly proved than many a
legend which has assumed the character of history in the hands of man;
for the geological record is the work of God.

Placed as the fossUs are in their several tiers of burial-places the one
over the other, we have in them true witnesses of successive existences,
whUst the historian of man is constantly at fault as to dates and even the
sequence of events, to say nothing of the contradictory statements which
he is forced to reconcUe.

In this volume I have passed rapidly over the earliest stages of planetary
matter, for these must necessarUy be for ever involved in much obscurity;
and respecting the earhest condition of the crust of the earth, I simply
inferred it was then in so molten a state that no life could have existed.
The sketch of ancient nature consequently began with a description of the
oldest known stratified rocks in which traces of life have been detected.
The Laurentian rocks (chiefly gneiss) of IS^orth America, Britain, Bavaria,
Bohemia, and possibly of Scandinavia, forming the foundations on which
aU the other strata have been accumulated, were characterized as contain¬
ing specimens of the lowest grade of animal life, in the shape of a marine
Eoraminifer, the Eozoon.

It was then pointed out that the next succeeding deposits, or those of
Cambrian age, though of enormous dimensions, and often but shghtly
altered mud and sand, contained only the rarest trace of anjrthing higher
in organization than a Zoophyte.

Next it was shown that the following (or SUurian) formations exhibited
even in their very bottom-beds a considerable augmentation of animal life,
as shown by the presence of Crustaceans, Mollusks, and Zoophytes, occu¬
pying layers at similar horizons in the crust of the earth in very distant