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 interstratified 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 civilization 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 great that in the area of modern Britain alone very nearly one 

 thousand organic species — a thousand distinct forms 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 withdrawal 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 fully 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, similar 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 graduate 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 



