Ixii INTRODUCTION. 
In the progress of British Geology it was however found that the Lower Silurian 
sections were wrong in principle. The so-called Caradoc sandstone transgressed the true 
physical and palzontological base of the “Silurian System ;” and, by a mistake of classifi- 
cation, united together, under one name, two contiguous (but sometimes discordant) groups 
of two distinct Systems. And so far as regarded the typical Llandeilo Flag, the mistakes 
were still more fatal. It was put in an erroneous relation to the upper Bala group, by a 
positive inversion of the sections: and it was put in an erroneous relation to the Wenlock 
group by a misconception of the sections; which did not shew a consecutive and complete 
succession, but one which was broken and discordant. 
If these fundamental mistakes implied (as they unquestionably did) some change of 
classification and nomenclature, who was to suffer from this change? The author of the 
Cambrian series, or the author of the Silurian? Let common reason and common sense 
give the reply. I had adhered to, and followed out, an acknowledged principle; and I had 
at length derived from it—without any violation of physical evidence, or any want of com- 
pleteness in it—a good classification and a good geographical nomenclature. My friend 
deserted his principles when he found his sections wrong. He no longer pretended to esta- 
blish his nomenclature on true physical groups borne out by lists of fossils. But because he 
had described the Llandeilo fossils (which had by the great undulations of South Wales been 
brought from beneath the upper Cambrian group into a discordant contact with his true 
Silurian terrace) and called them by mistake Silurian; therefore all the older rocks, both of 
North and South Wales, were to become Silurian ! 
Thus, in violation ef all geographical propriety, he proceeded to incorporate all Cam- 
bria within the limits of his Silurian kingdom. In doing this he claimed as his own a 
country over which he had no right of conquest. And while doing this he turned the whole 
logie of Geology upside down:—by making the true nomenclature to precede, and not to 
Follow, the true classification of the physical groups :—and by establishing his scheme on fossil 
evidence alone, in those very parts of the descending series where, above all others, the 
sections were most difficult, and true physical evidence was most needed. I do not believe 
that I am at all distorting the facts by overstating them: and I must not dwell any longer 
on first principles, to which I consistently held fast; and which my friend, unfortunately, 
deserted—to the great retardation of English Geology, and the great subsequent damage of 
its classification and nomenclature. 
No great step (be its direction right or wrong) is ever taken in physical science without 
some show of reason. In the illogical (and finally the unjust) expansion of the Silurian 
nomenclature, the steps are easily uncovered. The Silurian groups were established on what 
was (at the time) supposed to be good and perfect evidence. The groups, from the Ludlow 
to the Llandeilo base, were then called “a System.” From the first, I objected to this 
application of the word “System” for several reasons; but chiefly because the Bala fossils, 
so far as I knew them, were identical with species of the “Lower Silurian” groups. This 
facet was known to the author of “the System,” though he still placed his Llandeilo Flag 
