INTRODUCTION. Ixxxi 
and the place and office of the May Hill Sandstone. In short, not only here, but in every 
part of the controversy, since it first began, he has argued on grounds which prove, that, 
however admirably he had worked out the physical and paleontological history of his own 
true Silurian groups, he had missed their true physical and paleontological base; simply 
because he was unacquainted with the true physical history of the older rocks of Wales, 
and their general discordancy of position, when brought into contact with the overlying 
Silurian rocks*. 
Let me. however, in drawing this Introduction to a close, distinctly express my dis- 
sent from such assertions as the following: “That the Upper Silurian rocks are brought by 
conformable folds into proximity with the Llandeilo formation of South Wales” (p. 79) ;— 
“that the typical formation of the Caradoc Sandstone gradually passes into the Wenlock 
and Ludlow rocks” (p. 82) ;—“that the typical sandstone of Caer Caradoe dips everywhere 
conformably under the Wenlock shale” (p. 83);—‘ that the operations which, in some 
places, have produced a break between Llandeilo and Caradoc formations, had no én- 
Jluence whatever in destroying the races of animals” which belonged to the old period 
(p. 88) ;—*“that the black Malvernian schists (with Olenus, &c.) may be as old even as 
the Lingula beds of North Wales” (p. 92) ;—* that in some tracts we must expect to meet 
with links, lithological and zoological, which bind together the inferior and superior divi- 
sions of the System,” or in other words, the two Systems Cambrian and Silurian (p. 97). 
I might easily double the list of passages to which I could take an objection: but they all, 
or nearly all, merge under the one fundamental error which virtually appears to be admitted 
in Appendix B (p. 490). Now I had, as above stated, corrected this fundamental error 
of the “System” nearly two years before the publication of “Siluria.” Not to notice this 
correction in Chapter rIv., or not to cancel the errors, if Chapter Iv. was, in fact, written 
before 1852, was not to deal well with the public. It was virtually teaching the student 
to prejudge a question, in long debate, before the most important facts of evidence had been 
* In illustration of what is above stated, I give in this note an example of that strange spirit of advocacy which runs 
through so many pages of “ Siluria.” At p. 72 the author, while describing the section of Noedd-Griig, writes as follows, 
“Tt is gratifying to me to observe that this diagram (from the Government Survey) is quite in accordance with my old, 
published, coloured section across the same tract.” (Si/, Syst. p. 352, and Pl. XXXIV. fig. 3.) Would not any plain, 
unprejudiced reader conclude, from these words, that the interpretation of this section, by the Government Survey, was 
quite in accordance with the previous interpretation of the same section in the Silurian System? Yet the two interpret- 
ations are very widely apart. In the Silurian section the descending order is as follows: (1) Old Red Sandstone, 
(2) Upper Silurian Rocks, (3) Caradoc Sandstone of Noedd-Griig, (4) Llandeilo flags, passing into Cambrian rocks, 
(5) Cambrian rocks. The first three subdivisions of the section, thus interpreted, may be in a right order; though I 
believe there is no true Caradoc Sandstone at Noedd-Griig. It is probably May Hill Sandstone. There is no Llandeilo 
flag whatsoever (in the sense in which the words were used in 1839) answering to group (4); consequently there is no 
passage (like that described) into Cambrian rocks. If the typical Llandeilo flag of the Towy exist at all in the line of 
the section, it must be sought for, about five thousand feet further down, among beds not brought out in the section. 
Had the author succeeded in interpreting this section correctly, he would in so doing have destroyed his own order of 
superposition in the valley of the Towy—he would have destroyed the order of the fundamental and typical groups 
from which the Lower Silurian nomenclature derived its existence. The Government Surveyors saw this consequence, 
and got rid of it by a novel process of development—by designating the great Upper Cambrian series of South Wales 
under the name of cne mistaken Silurian group—(Llandeilo flag). And this is to pass as an improvement upon, or a 
correction of, my Cambrian nomenclature! 
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