POSTSCRIPT TO THE INTRODUCTION. XCVil 
there have been local dislocations during all geological periods. I accept, without reserve, 
many of the statements given, on this subject, by Professor Phillips (p. 119). But the 
grand disturbance of the older Paleozoic rocks of England marks the separation between 
the Cambrian and Silurian groups, as defined in the Tabular View. The N.E. and S. W. 
strike of the British Isles is the characteristic Cambrian, and is by no means the 
characteristic Silurian strike: although the May Hill and Wenlock beds, from having been 
deposited on Cambrian rocks, which have a N.E. and 8. W. strike, are partially affected 
(spite of all subsequent disturbances) by the strike of the old rocks on which they rest. 
Professor Phillips very properly notices (Manual, p. 120) the prevailing north-eastern 
strike of many of the greater mountain-ranges of the British Isles. But when he adds, “that 
all these chains were thrown up, though not exactly to their present height and aspect, after 
the termination of the Silurian ages and before the deposition of the Old Red Sandstone,” 
his statement, if not erroneous, is at least incomplete, and might therefore mislead the student 
of geology. That there is a great break in many parts of the Palsozoic series at the base 
of the Old Red Sandstone is certainly true: but in many parts of England the trwe Silurian 
rocks below the Old Red Sandstone have not, even approximately, a N.E. and S. W. strike. 
There is, however, another great break at the base of the May Hill Sandstone; below which, as 
a good general rule, the English rocks have the old north-eastern, or Cambrian strike. That 
these older dislocations extended into South Wales there can be no doubt: and they help us 
to explain the perplexing and discordant junctions of certain Cambrian and Silurian rocks in 
Radnorshire and Caermarthenshire. Among other causes, it was a want of knowledge of this 
fundamental fact which led to the first mistakes of classification among the lower groups of 
Siluria. I fought my way, single-handed, to a knowledge of the Cambrian Series which is 
sketched in this Introduction; and I have defended my classification single-handed, and 
without any fear of consequences; only because I have had to contend with opponents who 
had adopted a premature nomenclature before they were adequately acquainted with those 
great physical facts which are the basis of every good original classification, and without which 
a good geological nomenclature is impossible. 
At pp. 105 and 106 Professor Phillips copies from the works of Hall (the great American 
paleontologist), that magnificent series of deposits which extend, in North America, from our 
Devonian series down to the Lingula beds, or Potsdam Sandstone; and gives the English 
equivalents on the combined authority of Lyell, Sharpe, De Verneuil, and Murchison. But all 
these authors examined the question of the English equivalents while they were under 
the influence of a classification and nomenclature which (so far as England is concerned) is 
unquestionably erroneous. I should endeavour to compare the Oneida conglomerate 
(No. 8 of Hall’s Series) with the conglomerates of South Wales which are high in the Upper 
Cambrian series; and the A/edina Sandstone (No. 9) with the May Hill Sandstone, or the 
English Silurian base. I should not, perhaps, have ventured to throw out such a speculation 
as this, against the authorities above quoted; had I not learned, from Professor H. Rogers, that 
there was, in many large tracts of North America, a break in the older Palaeozoic series exactly, 
i 
