PAUEOZOIC OR PEIMARY. 



^im 



<! "':!:!!'i!;!'!> <: 



FOSSILIFEROUS OR 



The various strata composing the stratified or fossiliferous rocks, although frequeni 

 presenting the same mineral character, have a definite and constant order and arrangeme 

 which is never inverted. Thus, a group of strata in England, characterized by a certain set 

 fossil remains and overlying another group containing a different set of fossils, are never fou 

 in other countries to underlie the latter; the position of strata in relation to each other i 

 therefore uniform and invariable, and upon this uniformity depends the practical and ecoi 

 mical bearings of Geology. 



The sedimentary rocks are those which include the remains of animals and vegetables, m< 

 or less abundantly, and are hence termed the fossiliferous rocks. They are generally eitl 

 arenaceous argillaceous or calcareous deposits, which owe their origin to the agency of wat 

 being formed within the bed of the sea, or at the bottom of freshwater streams or lakes, 

 indicated by the nature of the contained remains ; with which also are sometimes associal 

 land plants, showing that a terrestrial surface existed at different periods, and from I 

 destruction of a portion of which, the sandy and clayey beds were probably derived. 



The stratified rocks are for convenience divided into three great series, according to th 

 relative antiquity, and the fossil remains found in them, which materially differ and are read 

 distinguished from each other; and they present three great life periods, to which the ten 

 primary, or palaeozoic; secondary, or mesozoic; and tertiary, or cainozoic, have been appliec 



PALAEOZOIC, OR PRIMARY SERIES. 



The primary series, overlying the metamorphic rocks, constitute with them some of 

 most elevated and picturesque scenery of the British Isles, as in Cornwall, North and Soi 

 Wales, the district of the Lakes, Scotland, and a large part of Ireland. From the frequ 

 association of igneous rocks with some of them, they have undergone considerable change i 

 induration, and are in this respect allied to the metamorphic rocks in fact, the orclin: 

 roofing slates so extensively quarried near Bangor, and previously alluded to, form a mem 

 of this series. Like the metamorphic rocks also, they contain many valuable deposits 

 mineral wealth. Fine marbles are obtained from this series; and the durable magnesian Lii 

 stone used in constructing the Houses of Parliament, belongs to the permian group. Besi 

 the valuable substance, coal, the carboniferous group contains rich deposits of iron ore and 1( 

 The Cambrian Rocks include a considerable thickness of schists, sandstones, and c 

 glomerates, as the Harlech grits, and the Llanberis and Longmynd strata. They are nef 

 unfossiliferous, only a faint trace of organic remains having been detected in them in Irel 

 Some geologists include an upper and more fossiliferous series, as the Lingula and Trema 

 beds of North Wales, which are considered by others to form the lower zone of .the next grc 

 The Lower Silurian group, including the upper beds just mentioned, and the Cara 

 sandstones and Llandeilo flags of Wales, constitute a series containing many fossils. T 

 have been traced in Wales, 'Cumberland, Scotland, Ireland, France, Spain, Germany, Russia, 

 The Upper Silurian group were first described by Sir R. Murchison, and include the 

 stones, Lucllow group, and Wenlock and Woolhope strata, and are marked by a gre 

 develo pmentof limestone, containing a large series of fossils. 



The Devonian, or Old Red Sandstone, presents two aspects, one that of Scotland and 

 border counties of Wales, consisting of coarse conglomerates, sandstones, and impure li 

 stones, locally called cornstones, and containiug many peculiar fishes; the other, tha 



LONDON: PUBLISHEE 



