SUPPLEMENT TO THE INTRODUCTION. IXxxix 
Silurian nomenclature, beyond its true base, was commenced, and has been followed out, by 
the abandonment of the very principles on which every true Silurian group was first 
established and became accepted by geologists. Hence I confidently affirm, that so far 
as there is any contest between my opponent and myself, it is by no means a question of 
mere expediency about the retention of certain names; but it is a question of principle—a 
contest for a Cambrian nomenclature which is geographically, historically, and palzeontologi- 
cally right, against another nomenclature which, on all these grounds, is positively wrong. 
I think that I have succeeded, in the previous pages, in pointing out the origin of 
the erroneous nomenclature adopted in 1843 by Sir R. I. Murchison; and from him, 
unfortunately, by the gentlemen of the Government Survey. I say unfortunately, because 
their adopted nomenclature led them into the mistake (the greatest they could have com- 
mitted in the actual state of our knowledge of the Paleozoic groups) of confounding the 
May Hill Sandstone with the Cambrian beds of Horderley, and of uniting them together as 
a (so-called) “ Middle Silurian group.” Be this as it may, it is at least true that the original 
groups and sections, from which the Lower Silurian nomenclature was derived, turned out to 
be erroneous. ‘The first mistake of nomenclature was in degrading the “ May Hill rock” from 
its true place at the base of the Silurian System, and substituting for it the Caradoe (or 
Horderley) sandstone. The “ May Hill rock” of Murchison I have restored to its right place 
and office. The Caradoc sandstone is made up of two discordant groups, belonging (if 
we use the Silurian language) to two distinct systems. The grand mistake, however, was in 
placing the Llandeilo Flag above my Upper Cambrian group, which was based on the Bala 
limestone. If the Lower Silurian groups were physically and sectionally wrong, the nomen- 
clature derived from them could not be right. How, then, was it to be amended, or to 
be so amplified as to fall in with the true physical development of the Cambrian series? 
Mr Sharpe led the way in the attempted solution of the difficulty; and in 1842 he instructed 
the Geological Society that this grand error of the Lower Silurian sections “ had been adopted 
by Mr Murchison on the authority of Professor Sedgwick”—that all the older fossil-bearing 
rocks of Wales were Caradoc sandstone—and that, collectively, they were not thicker than 
Caradoc and Llandeilo formations of the published Silurian Sections ! 
Had all this been true, I should have no true ground for complaint of injurious treatment 
on the part of the Geological Society, or of injustice on the part of Sir R.I. Murchison. I have 
little doubt but from that year, and for some years afterwards, a majority of those who formed 
the Council of the Geological Society believed that a great blunder had been committed, and 
that I had been the blunderer. The statement of Mr D. Sharpe was not however historically 
true. It was unintentionally, but not on that account the less directly, contrary to fact; and 
only proved how imperfectly he had become acquainted with the physical structure of Wales, 
and with the previous history of the Society. 
The unintentional historical misstatement was not by any means set right, as it ought to 
have been, by the author of the “Silurian System.” On the contrary, he silently turned it 
to his own advantage; and after some other statements on his own part, upon which I have 
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