INTRODUCTION. xlvii 
that my sections, made in 1831 and 1832, and exhibited in 1838, were perfectly right in 
principle, and generally right in detail. What then became of the Lower Silurian groups? 
They became absolutely baseless; and so far as they were concerned, the Silurian nomencla- 
ture had not the evidence of one true and well understood geological section to rest upon*. 
During the eight summers which elapsed after 1834, I was employed in exploring the 
paleozoic rocks of England, so far as my engagements and health permitted. Four years 
I spent chiefly upon the Devonian series, and in accumulating evidence for its establish- 
ment. This long, and not unprofitable task, was first undertaken as a joint labour by 
Murchison and myself in 1836. In the two following summers I was a solitary labourer 
in the great Devonian field, with the exception of very valuable help I occasionally had 
from the present secretary of the Geological Society (Mr Austin), It is not true (as I 
have been told) that I ever deserted the great Paleozoic field. As soon as my engage- 
ments would permit I went over (in 1841, 1842, and 1843) what appeared to be the 
best Devonian, Silurian, and Cambrian ground in Ireland, in Scotland, in a part of Cum- 
berland, and in North Wales. While crippled in 1844, my friend Salter became my 
representative; and he endeavoured to carry our joint work onwards into a part of South 
Wales, so as to ascertain the relations of my higher Upper Cambrian groups to the Llandeilo 
group of Builth. At that time I suspected (as it was then almost certain that the two 
“Lower Silurian” groups had been put in a mistaken relation to the Upper Bala rocks) 
that many of the great undulating groups of South Wales would prove to be “ Upper 
Silurian.” But no satisfaction was gained as to this point. 
In 1845 and 1846 I was again toiling among the Cambrian and Silurian rocks of the 
North of England and of Wales—not to maintain any hypothesis, but in the search of truth— 
seeking to establish a real succession of groups, and a co-ordinate succession of fossils, such 
as might be the foundation of a true and consistent classification and nomenclature. The 
traverses | made, with my friend John Ruthven, in 1846, proved that I was mistaken in 
my expectation, that a considerable portion of the old undulating groups of South Wales 
would prove to be “Upper Silurian.” The gentlemen of the “Government Survey were at 
that time working out the details of the South Welsh sections, near the junction of the 
Llandeilo and the true Silurian groups. I therefore spent little time upon the sections, 
thinking that they were in better hands than mine; and after collecting a series of fossils 
along the valley of the Towy, I left that part of Wales, never expecting again to return 
to it. 
The reader may well ask why I have given this short chronological narrative in my 
Introduction to the Cambridge Palzeozoic Fossils. I have done so for the sole purpose of 
repelling an assertion that I had at one time deserted the Paleozoic field and abandoned 
* The sections of Builth and Corndon are well and elaborately described in the “Silurian System:” but they are 
put in an erroneous relation to the “ Upper Cambrian” group ; as is proved by the name, Llandeilo, which is given to their 
fossiliferous beds. If the typical Llandeilo flag of the valley of the Towy be in a false relation to the Upper Cambrian 
rocks, the Llandeilo rocks of Builth and Corndon must ineyitably partake of the same error. Rocks with a common name 
must have common geological relations. 
