Ixxx INTRODUCTION. 
In the previous discussion I have been arguing at a great disadvantage ; for the question, 
between the Cambrian and Silurian nomenclature, ultimately turns upon the establishment of 
the May Hill group. In missing the elimination of that group, my friend missed that 
which was essential to his own System; and everything he did below the May Hill group 
was affected by this one fundamental error, which vitiated his sections and put the whole 
scheme of his nomenclature (so far as regarded his lower groups) in direct antagonism 
with the development of nature. For his scheme, when followed out, became not only 
geographically monstrous, and sectionally untrue; but after the May Hill and Horderley 
beds had been placed (as nature had placed them) in two different Systems, the scheme 
became also paleontologically untrue. Enough has been stated on this subject in the pre- 
vious pages of the Introduction. 
It does, however, appear strange, that while writing the fourth chapter of “Siluria,” 
published in 1854, the author should have overlooked a correction of vital consequence, 
made nearly two years before by Professor M°Coy and myself (1852). The author of 
« Siluria’’ was present when this correction was made in a paper read before the Geolo- 
gical Society. He probably did not believe in our elimination of the May Hill from the 
Caradoc group: for it was opposed, strenuously though courteously, by the gentlemen of 
the Government Survey who were present. But it was adopted by four of them (in- 
cluding their two best paleontologists), within a period of about five months* after my 
paper on the May Hill sandstone was first read. 
Whatever may be the cause, the fourth chapter of “Siluria” has errors of no small 
magnitude (sectional or paleontological) in almost every page; and it is pretty clear, from 
his Appendix B, (p. 490) that the author is now aware of them; though not of their whole 
extent and real importance. 
Formally to catalogue and discuss these mistakes would be both an invidious and a 
useless task; for they all arise, by direct implication, from the fact, that the author, while 
writing the fourth chapter of his new work, overlooked the determining facts of the whole 
the physical meaning of the Upper Cambrian (or Caradoc) conglomerates, 
controversy 
grave geological error in determining the place of his lower groups, he is not on that account called upon to change his 
geographical nomenclature. On the contrary, that the geographical names of the Principality are to be changed, in order 
to bear out a nomenclature, which was, from the first, erroneous, because based upon erroneous sections. I know of 
nothing more anomalous in reasoning, and more geographically monstrous, in the history of science. This appears to 
me only a plain unvarnished statement of the question; in which any argument, on the grounds of priority, is left out of 
sight, however greatly it adds to the real truth and equity of the question. 
* The reader of the Proceedings of the Geological Society of London is requested to attend to the dates of the 
papers on the May Hill Sandstone. The printing of my first paper on that subject was postponed by the Council without 
any satisfactory reason given to myself; and, if I am not misinformed, against the advice of the first Referee. Mean- 
while two papers on the same subject, by two gentlemen of the Government Survey, were very properly printed without 
delay. The consequence was, that their papers appeared before mine, though they were read several months a/ter it. 
Mine was a very short and simple statement, and ought not to have been postponed; especially as it related to a 
new and controyerted question, upon which, as the event proved, I was perfectly in the right. 
