346 
THE GEOLOGIST. 
The age of the world, then, which we have been considering, was 
comparatively a very early one ; prior to the growth of that flora of 
unparalleled luxuriance which has been transmuted into coal, and the 
deposition of the iron-stone so frequently, and in such abundance, 
found inter stratified with the coal-beds ; a period earlier than that 
in which were elaborated and localized so very much of the materials 
containing that force, and strength, and durability which give a form 
and character to the civiHzation of our own times ; — anterior to those 
pages, at once historical and predictive, in which was pre- written so 
much of the history of countries and nations then very remotely dis- 
tant in the future, and seen only by the eye of Prescience. 
Yet it was by no means the infancy of the world ; it had been pre- 
ceded by times of vast duration, represented by miles, in thickness, 
of sedimentary rocks ; all necessarily presupposing denudation, and, 
therefore, an equal amount of still more ancient rocks ; earlier times 
so gTeat that in the area of modern Britain alone very nearly one 
thousand organic species — a thousand distinct fonns of life — had 
performed their parts and passed into utter extinction ; not only 
species, but genera, families, and even orders had entirely passed 
away ; the world had already become old to, and for, them ; the ex- 
ternal conditions to which they were adapted had disappeared, and 
had compelled their Tvathdrawal also — gradually, slowly, and succes- 
sively ; whilst their vacated niches were, one after another, occupied 
by new forms adapted to the new circumstances. 
That the age was itself one of incalculable duration is evidenced 
by the facts that in some localities it is measured by folly two miles, 
vertical, of sedimentary matter, eminently and unmistakably detritai ; 
and in others by vast piles of limestone, the result of the slowly 
constructive labours of the small coral polype. If we may assume 
that then, as now, reef-building corals did not labour in depths ex- 
ceeding from twenty to thirty fathoms, we are furnished with a 
sounding-line that enables us to fathom seas that no longer exist ; 
and since, in some instances, those limestone beds make up an aggre- 
gate thickness very greatly exceeding this, yet every stratum clearly 
the product of long- continued polype labour and industry, it appears 
that the Darwinian hypothesis of areas of slow and long-continued 
subsidence which so felicitously explains the phenomena of the coral- 
reefs of the Southern ocean, is equally applicable to, and equally 
required for, similai phenomena in the British area during the Devo- 
nian age of the world. - 
That it was a distinct organic period is seen by its fossils, for the 
most part peculiar and characteristic, yet intermediate in general 
facies to those of the Silurian and Carboniferous ages ; but it was 
not isolated from either, as some of its forms of life were derived 
from the former and a still greater number transmitted to the latter : 
the three great Palaeozoic periods gTaduate into one another, blending 
as softly as do the tints of the rainbow, and emphatically deny that 
from the commencement of the first to the termination of the last 
