xlvili INTRODUCTION. 
my proposed Paleozoic nomenclature. The task I had on hand was incomparably the 
hardest in British Geology, and I never thought of abandoning it; and as for nomenclature, 
I had no cares about it; and I was ready, at every turn, to modify or change it, in any 
way compatible with truth and reason. What I have done, since 1846—in Scotland, 
Yorkshire, and Westmoreland ; in Cornwall and Devonshire; in making out minute points 
of detail on the junction line of Cambria and Siluria; and in establishing the May Hill 
sandstone as a distinct group—is work too recent to require a notice here*. But all of it 
was destined to the same important end—the right classification of the British Paleozoic 
rocks. I am not able now to labour as I did in former years; but I never abandoned 
my task; and it is at length as complete as I can make it. Its condensed results are given, 
so far as regards classification, in the Tabular View. 
Should any one ask whether I ever doubted, between 1834 and 1842, about the integrity 
of the “Lower Silurian” sections, I should reply, that I doubted about the geographical 
propriety of certain parts of their base line, that I could not reconcile them with the upper 
groups of my own sections; that I always objected to the name system being given to the 
Silurian rocks from the Upper Ludlow to the Llandeilo group; and that I did so partly 
on physical and partly on paleontological grounds. 
Sometime after 1834 (I believe in 1836) I submitted a small collection of about 
twenty very characteristic and abundant Bala species to Mr J. Sowerby. He could not 
find among them one single specimen that he had not before among his Lower Silurian 
fossils. Here was matter for some misgiving: for if the “Lower Silurian” sections (which 
had been discussed over and over again at the Geological Society) were right, the Llan- 
deilo group was at the least five or six thousand feet above the Bala limestone. This 
fact respecting the Bala fossils was published by myself at the beginning of 1887. 
* The term May Hill Rock was used by Murchison (Jan. 1834) instead of Caradoc, a term introduced afterwards by 
himself. In using the terms May Hill Sandstone, I have not innovated in nomenclature, but, on the contrary, have 
restored an old Silurian name to its right place and office. The scheme of classification then given by my friend (Pro- 
ceedings of the Geological Society, Vol. 11. pp. 13, 14) would be nearly correct were the May Hill beds struck off from the 
Horderly group and packed at the base of the Wenlock group; and were it stated, also, that the Llandeilo Rocks were, 
on one side, unconformable to those of the Longmynd. But in the same paper the Longmynd Rocks are placed on the 
same horizon with the undulating series in the hills west of Llandovery. This mistake he afterwards corrected: but the error 
in placing the undulating rocks of South Wales to the west of Llandovery (my Upper Cambrian group) below the Llandeilo 
group was not corrected ; nor was it apparently suspected. Thus two years afterwards (Jan. 1836), he stated “ that in a portion 
of the preceding summer he had been employed in tracing these rocks (the ‘Cambrian System’) from Caermarthenshire 
into Pembroke; and in doing this he was led to attempt a general survey of the country, examining the strata from the 
youngest to the oldest; dwelling, however, especially on the deposits of the ‘Silurian System.’” 
Again, in the abstract of the same paper (Proceedings, Vol. 1. p 229) he separates the Cambrian system into three 
subdivisions, in the lowest of which he places the Longmynd rocks: and while describing the rocks composing the highest 
of the three subdivisions (my Upper Cambrian Group) he uses these words; viz. “They occupy a great breadth; and, as in 
Cardiganshire, they form the beds of passage between the Silurian and Cambrian systems—sometimes without a break.” 
How was it possible for me, or for any one else (after such statements, and after the repeated exhibition of the detailed 
Silurian Sections to the Geological Society), not to believe that the Lower Silurian Groups were superior to the rocks 
I called Upper Cambrian? If this belief was founded ina great geological mistake, let me not be blamed for it; and let 
its consequences rest with its author. It was not ccrrected, but was reaffirmed when the “Silurian System” was published 
in 1839. 
