SUPPLEMENT TO THE INTRODUCTION. 
Trinity CoLtEce, July, 1855. 
AFTER a very long delay the Introduction has passed through the press, and the whole 
of it is now before me. It was commenced late in the October Term of 1854, and was con- 
tinued without delay to the end of the Tabular View (p. xxvi), when I became incapable, from 
a long illness, of making any further progress with it. At the beginning of March (supra, 
note to p. xxvi) I resumed my task, which was painfully carried forward through about thirty 
additional printed pages, when I was again reluctantly compelled to suspend it. The last 
four or five sheets have, in consequence, been printed from MSS. sent, from time to time, 
from Norwich (during my Cathedral residence of May and June), when I was without any 
works of reference except a copy of “Siluria.” I fear, therefore, that some portions of 
the Introduction are less perfect than they ought to be, and that some useful, and per- 
haps needful, references may have been omitted*. Thus, ¢.g., after glancing the eye over 
the Introduction, I found that I had quoted (p. Ixxii) an assertion, made by Mr D. Sharpe 
in 1842, without giving, at the same time, a proper reference to his paper. The sentence 
quoted is found in the “Proceedings of the Geological Society of London,” Vol. rv. p. 10. 
An Essay, written and printed during the lassitude of a long-continued illness, many 
times interrupted, and at length finished under a pressure of engagements quite foreign to 
geology, is inevitably wanting in a true unity of plan, and I have to ask the reader's 
indulgence for some clumsy verbal repetitions which ought to have been avoided; and in 
some of the more lengthened arguments I have so far repeated myself, that I appear while 
writing at Norwich to have partly forgotten what had been, some months before, written 
at Cambridge. I have also to request the reader’s indulgence for some verbal mistakes, which 
will be corrected in the list of errata, when the mistakes materially affect the meaning of 
the text. 
So far as the Introduction is historical it is, I trust, literally true. So far as it is 
argumentative it is, no doubt, the plea of one who is his own advocate ; but it is, at the 
same time, the plea of one who is acting on the defensive, and who firmly believes that he 
is vindicating the cause of common justice and common sense, as well as of scientific truth. 
I never abandoned my Cambrian nomenclature after I had adopted it; but I never 
refused to modify it so that it might meet the requirements of an advancing science. That 
it has been misunderstood, misrepresented, and very ignorantly tampered with, is as certain 
as any fact in the past history of Geology. From first to last, the classification and nomen- 
clature, given in this Introduction, have been followed out on the same principles on which 
English geologists have established the classification and nomenclature of all great collective 
groups,—whether Primary, Secondary, or Tertiary. On the contrary, the extension of the 
* Some of the references, here alluded to, haye now been supplied in the note appended to the Introduction (p. Ixxxv). 
