lii INTRODUCTION. 
abandonment, on my part, of the very principles on which the “Silurian System” put in 
its claim for our acceptance. For, it professed, from first to last, to be grounded on 
the evidence of superposition, fortified by corresponding groups of fossils: and if, in its 
lower groups, it failed in that kind of double evidence; then the ground on which it rested 
was struck from under it, and it ceased to have any meaning as a real system. 
It would ill become me to torture, beyond its meaning, the opinion expressed by my 
friend respecting the age of the Bala limestone, when we were, for the last time, together 
in North Wales (1834). But I may remark, that it was an opinion fairly derived from a 
true and unambiguous section, that it was delivered on a vital point of evidence, and that 
it throws a clear light upon the original meaning of the words Cambrian and Silurian when 
they were first made use of. This, at least, I do affirm without reserve, that if any doubt 
as to the soundness of that opinion ever afterward rose within the mind of my friend, it 
ought in fairness to have been communicated to myself before he had proceeded to incor- 
porate Cambria in Siluria*. 
The only legitimate questions which can arise in this concluding part of the Intro- 
duction are such as the following: viz. Is the analysis of the Cambrian Series right in 
principle? Are the successive groups of the Tabular View in a true order of superpo- 
sition? I have no doubt of the general truth of the analysis, not only because it is the 
result of observations of my own, long continued and made with no common toil; but, also, 
because it was most critically and severely sifted, during the last two meetings of the British 
Association, without being invalidated on any one essential point. During the meeting of 
1854 my scheme of classification and nomenclature was met by some distinguished geolo- 
gists, and especially by the gentlemen of the Government Survey, in a spirit of direct 
antagonism; but not one of my antagonists convicted me of error in a single group of 
my Tabular View. It was acknowledged that the analysis of the Cambrian Series, in the 
Tabular View, was substantially right; and that I was the first person who had worked out 
the analysis. Lastly, it was admitted by the President of the Geological Section (once my 
opponent on the very point) that the May Hill sandstone was a true physical and pale- 
ontological group, occupying the place I had given it in the general section. 
I therefore conclude :—First, that the analysis given in the Tabular View is right and 
true. Secondly, that the nomenclature proposed is on an accepted and right principle— 
being based on true sections, and also (so far as the case admits of it) on the co-ordinate 
evidence of fossils. Thirdly, that—so far as regards the lower groups of the Lower Palzozoic 
* Had my friend discovered for himself the mistaken relations of his lower groups; then corrected his mistakes ; and 
afterwards (by traverses through North and South Wales) shown that the Llandeilo flag was nearly on the parallel of the 
Bala limestone—he would by so doing have vindicated his claim (not as a matter of courtesy, but of right) to a share in the 
Upper Bala Group. But he did none of these things. He found that his own Lower Silurian work was wrong, by the 
gradual progress of geology; and to save all further difficulty he proceeded, without any notice, to merge all Cambria in 
Silurial! This might be a ready way of saving a nomenclature which he had extended to foreign lands. But it neither 
recognised the mistakes of the Silurian sections, nor gave us a true and congruous English nomenclature, nor was it just 
toward myself. 
