Ixxiv INTRODUCTION. 
that I did not mislead him—that he adopted no part of his order of superposition on my 
authority. He gave me no opportunity in 1834 of correcting his Silurian base, or of 
removing the Llandeilo group into its right place in the Cambrian Series. Had we made the 
attempt, we might, perhaps have failed, while together, as he had done while toiling by 
himself; and we might have failed mainly for this reason—that it is far easier to advance 
in the way of truth from a state of ignorance, than it is to correct an error which has 
been put forward on authority and received as an established fact. Be this as it may, 
it has nothing to do with the present question in debate. For full twelve years I never 
touched the Llandeilo country after 1834. The author of the “Silurian System” had the 
game in his own hands; and he continued so to deal with it, as to put his two lowest groups 
in an absolutely false relation to the Upper Bala groups both of North and South Wales. 
Again, on the East side of the Berwyns I accepted, provisionally, his erroneous inter- 
pretation of the fossiliferous groups, and thereby damaged the integrity of my own sections, 
which were perfectly right in principle. And lastly, (in 1834) I did not blink a single 
difficulty; but I shewed him the Bala limestone, and explained to him its true relations, 
which he accepted, and which he interpreted correctly. He did not tell me that I must 
pause till I had produced a set of organic remains from the Bala group, “differing as a 
whole from those which afterwards appeared in his classified and published Silurian System.” 
He did not tell me “to wait for the production of a set of new typical fossils:”? but on 
the contrary, guided, and very properly guided, by the physical evidence, he called (so 
soon as the nomenclature was agreed upon) the Bala group, as well as its equivalents in South 
Wales, Upper Cambrian. And if the Upper Cambrian groups of South Wales were, as he 
had placed them, below his Llandeilo Flag, the Bala limestone must be at the very least 
five or six thousand feet below it. 
Here, no doubt, was a great difficulty; which arose, as the event proved, from a great 
mistake. But who had made the mistake? The author of the “Silurian System,” and no 
one else. My Bala sections were perfectly correct. And, I repeat, that if during the eight years 
which elapsed after our joint examination of the Berwyn sections in 1834, my friend hada 
single doubt about the correctness of the nomenclature agreed upon, he had no right in 
courtesy to introduce a change of names without some communication with myself. Still 
less had he any ground in scientific truth to change his principles of classification ; by putting 
out of account his own very great mistake (to the fatal damage of a consistent geographical 
nomenclature), and by throwing the sole responsibility of it on myself. 
To have written with common historical fairness, my opponent should not have used 
such words as I have quoted from his “Siluria,” p. 7. He ought to have stated that he 
had mistaken the relations of the lower groups which he had classified and published in 
the “Silurian System.” That by accepting this classification “his friend and fellow-labourer ” 
had unfortunately been misled. That the Upper Cambrian rocks were not below (as they 
appeared in his published Silurian sections) but above the base line of his Llandeilo group. 
That he had described the fossils correctly, though he had mistaken the sections; and, 
