Chap. I.] 
GENERAL PALAEOZOIC SUCCESSION. 
15 
Keverting now to the Silurian region proper, in which those researches 
began which enabled me to prepare the ' Silurian System/ I take leave of 
the Laurentian rocks with the expression of my belief that they have no 
existence in England and Wales, nor, as far as I know, in Ireland*. 
The most zealous researches of collectors and palaeontologists during the 
last quarter of a century, though pertinaciously directed to this point, have 
failed in detecting any other traces of former life in the Cambrian rocks 
than the few relics which will presently be described — albeit in a large 
portion of their range the Cambrian strata of the Longmynd, having an 
estimated thickness of 26,000 feet, are very slightly altered. No sooner, 
however, do we examine the deposits formed subsequently than we meet 
thenceforward with a never-failing storehouse of organic remains. 
In the lithograph given in the Frontispiece, repeated from the former 
edition, there is an attempt to represent, by colour and indications of stra- 
tification, the succession of the most ancient rocks as seen in looking west- 
ward from Inchnadamff on Loch Assynt in Sutherland. Thus the low distant 
hills forming the sea-coast consist of that fundamental or Laurentian gneiss 
(a) which is older than any rock in England and Wales. . Next, the lofty 
mountain of Queenaig, composed of horizontal, chocolate -coloured, hard 
sandstone and conglomerate (b), is of the same age as the Cambrian rocks 
of the Longmynd in Shropshire, and Harlech in Wales, which, as will pre- 
sently be shown, lie beneath the whole of the Silurian strata of Wales and 
England. The overlying sloping masses descending into the foreground 
are quartzites or altered sandstones (c 1 and e 3 ), with included crystalline 
limestones (c 2 ) ; and these (when they range into Durness) contain about 
twenty species of Lower Silurian fossils f. 
After a short sketch of the earliest or Cambrian zone of sediments 
of the Silurian region, full descriptions will be given of the Lower and 
Upper Silurian rocks. Other chapters will treat of the strata (now 
termed Llandovery rocks) which unite the two groups, and of the up- 
per members of this great natural series. Whilst so separated for 
purposes of classification, it will, however, be clearly shown that, 
through their organic remains, these deposits comprehend but one great 
system of life. Condensed accounts will then follow of the overlying or 
* Inasmuch as the Eozoon Canadense frequently tion of the belief that a marine creature of that 
occurs in serpentinous limestone, it was at one time class may have lived on from the Laurentian to 
supposed that it had been discovered in the green the Silurian era. Thus some of the Foraminifera 
marble of the Connemara Mountains in Ireland, represented by siliceous casts in the Lower Silurian 
In a future page it will be shown that this Irish green sand of Eussia (as will be noticed in the 
rock is of Lower Silurian age. Now, without sequel) are probably identical with existing 
entering into the controversy respecting the true species ; and Nodosarinae undistinguishable from 
character of the Eozoon, I may state that much living forms are found in the Permian limestones, 
ability was displayed by Dr. Eowney and Profes- Many others also have lived on from the Secon- 
* sor W. King, of G-alway, in their recent effort to dary periods ; and the same Grlobigerina that con- 
show that the forms of Eozoon which they exa- stitutes great masses of the Chalk now coats the 
mined were purely referable to chemical and bed of the Atlantic and other oceans, 
mineral conditions. On this point I will only say t These fossils, discovered by Mr. C. Peach, are 
that, believing, as I do, the Eozoon to be a Fora- described in the Mnth Chapter, 
minifer, I can see no valid objection to the adop- 
