INTRODUCTION. xxvii 
and by arguing for his classification, on perfectly new grounds of evidence (never so much 
as seen by myself), and thereby trying to convict me of an erroneous interpretation of the 
meaning of his Lower Silurian types. If this is to be called fair reasoning, and the language 
of an impartial historian, there is an end of the rules of philosophic evidence. It is, as I 
stated before, sheer advocacy; and if my views of right and wrong be not utterly con- 
founded, it is very transparent, and therefore very bad, advocacy. This may be called a 
harsh comment; but an unjust comment it is not, if plain words and plain facts are to 
retain their meaning. 
Anxious as I now am to bring this Introduction to an end, I must request the reader's 
attention to another extract (Siuria, p. 25): “The term ‘Cambrian’ is not used in this 
work because when introduced by Professor Sedgwick it was employed both by him and 
myself, as applying to a vast succession of fossiliferous strata containing undescribed fossils, 
the whole of which were supposed to rise up from beneath the well-known Lower Silurian 
rocks. The Government geologists have shewn that this swpposed order of infraposition was 
erroneous, and that all the fossiliferous rocks of North Wales, which had been called Cam- 
brian, before their included fossils were described, are physically the same strata as those 
which had been laid down as Lower Silurian on the immediate west flank of the funda- 
mental rocks of the Longmynd.” 
If this be not sheer advocacy I know not where I am to seek for it. It is true that a 
vast succession of fossiliferous strata (all the great collective groups of the Cambrian Series 
as given in the Tabular View) was supposed to rise from beneath the “Lower Silurian” 
rocks. But if this were a mistake, to whom do we oweit? To the author of the “Silurian 
System,” and to no one else. The mistake rested on his sole authority. And even allowing 
that the lowest Silurian group, by a monstrous process of development, might become the 
equivalent of the Upper Cambrian group (of all the Cambrian rocks above the Bala lime- 
stone); by no process of physical development could it be stated, compatibly with common 
truth, that the Festiniog slate, the Lingula Flag, the Harlech grits, and the magnificent lower 
slate-zone of Wales (Llanberris and Nant Francon slates, &c.) were the physical equivalents 
of the Caradoe and Llandeilo groups. It is not true that the fossils of the Bala group were 
unknown. Several species were known, and every known species was described as identical 
with species in the Lower Silurian lists. In the progress of discovery a peculiar group 
of fossils was found in the Lingula Flag; and it is, I believe, true that all the vast Cambrian 
Series (with the doubtful exception of its lowest group) is fossiliferous—though the number 
of species gradually diminishes as we descend. This is no new doctrine. And if we have a 
right so far to relinquish our first principles, as to classify the true Silurian Series by 
physical and fossil evidence combined, and then to classify and name the Cambrian Series 
on fossil evidence alone, we may give something like plausible evidence for the expanded 
Silurian nomenclature. This is incontestably the very ground on which the question was 
first argued both by the author of the System and the geologists of the Government 
Survey: and it was done while the broad fact was plainly standing up before them that a 
