476 
SILURIA. 
[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 accomplished ; 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 all 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 fossils are in their several tiers of burial-places the one 
over the other, we have in them true witnesses of successive existences, 
whilst 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 reconcile. 
In this volume I have passed rapidly over the earliest stages of planetary 
matter, for these must necessarily be for ever involved in much obscurity ; 
and respecting the earliest 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 North America, Britain, Bavaria, 
Bohemia, and possibly of Scandinavia, forming the foundations on which 
all 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 
Foraminifer, the Eozoon. 
It was then pointed out that the next succeeding deposits, or those of 
Cambrian age, though of enormous dimensions, and often but slightly 
altered mud and sand, contained only the rarest trace of anything higher 
in organization than a Zoophyte. 
Next it was shown that the following (or Silurian) 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 
