402 Murchison’s Siluria. 
Then it was, that positive proofs, derived from a wide field of 
observation, enabled us to commence geological history, with an 
account of the entombment of the earliest animals recognizable 
in the crust of the globe; and also to indicate the successive con- 
ditions which prevailed upon the surface, in a long series of ages, 
and during the many changes of outline which preceded the pres- 
ent state of the planet. Then it was, that looking to the whole 
history of former life, as exhibited in the strata, it was demon- 
strated from phenomena in one great empire alone (as had to a 
great extent been shown in Britain), that during the formation of 
the sediments which compose the crust of the earth, the animal 
kingdom had been at least three times entirely renovated ; the 
secondary and tertiary periods having each been as clearly char- 
acterized by a distinct fauna as the primeval series. In the work 
on Russia the sequence was thus followed oitt truly, from the 
most ancient fossil-bearing strata to the most recent stages in the 
geological series. 
In this volume attention is chiefly restricted to what has proved 
to be the protozoic, or first era of life. The plan, therefore, pur- 
sued will be, so far, similar to that which was adopted in the ear- 
lier chapters of the work on Russia; and these first leaves of ge- 
ological history will be written from the clear traces of a begin- 
ning,—a plan which, for want of knowledge, was impracticable 
in Britain when the “Silurian System” was publishe 
After a short sketch of the earliest and unfossiliferous sedi- 
ments, full descriptions will be given of the Silurian rocks (Lower 
and Upper), followed by very brief accounts of the three over- 
lying groups of paleozoic life, the Devonian, Carboniferous, and 
ermian. 
boniferous rocks. At that time, however, none of the fossil 
fishes of the Scottish or English Old Red had been found in the 
sandstones, slates, schists, or limestones of Devonshire, or the 
posed (although my fossils were first named and classified) that the Lower Silurian 
should be merged in the Cambrian. But, now that the terms Lower and Upper Si- 
; ve been adopted in every country, the question is settled. My deep regret 
is difference of opinion has been expressed in the Preface ; for 
in general views, as in private friendship, we are cordially united. 
