vii INTRODUCTION. 
Hence the author had no right whatsoever, on Paleontological grounds, to call his 
Silurian rocks a “System.” He had no right to throw out the word at random; with 
a reservation that he might afterwards make it good by a new and arbitrary act of 
incorporation of Cambria into Siluria. When he did this he virtually deserted those prin- 
ciples of classification and nomenclature which he had (above any other member of the 
Geological Society) helped to establish. I opposed his use of the word System whenever 
the nomenclature of his groups was discussed between us either in private or before the 
Geological Society. A System, however, they were called; and if he made his first mistake 
in adopting his name “Silurian System” before he had found its geological base, he must 
abide the consequence of the mistake, without making mea sharer in it. The facts I ex- 
hibited to him in 1834 might well have made him doubt about the truth of his own sections. 
His belief in the geological truth of his lower sections, does not, however, appear to have 
been shaken in 1839. Hence I contend (even on the admission that the lower groups of 
his Silurian Sections were rightly placed) that he was not a good and true instructor of 
nomenclature: on the contrary, that he overstepped the evidence given by the older British 
Paleozoic rocks, and positively misled the Russian geologists, when he taught them to 
describe as “Lower Silurian” every rock in which they found the “ Lower Silurian” fossils. 
The second great mistake was perhaps a natural consequence of the former. For if 
the author of the “Silurian System” had a right to call all foreign rocks—below the old 
Red Sandstone—Silurian, unquestionably all Cambrian rocks must become Silurian. But 
here the fundamental sophism, involved in the Silurian syllogism, became perfectly trans- 
parent; for the authors next step (when he sponged out the whole of his own base 
line, and coloured all Cambria as if it were but a part of Siluria) brought him into 
direct collision with another workman in the same field, who knew the Cambrian rocks far 
better than himself; and also into direct collision with his own lower sections, and the very 
evidence on which the scheme of his classification and nomenclature had any claim upon 
the acceptance of geologists. 
It was perfectly certain, before the Silurian map was changed (1843) and its colours 
spread over the older rocks of Wales, that some great mistake had been committed in 
the construction of the “Lower Silurian Sections.” <A great mistake there was; but its 
extent was, perhaps, not then known. The progress of discovery shewed that the Llandeilo 
group had (by the greatest and most mischievous mistake committed in the history of 
English Paleozoic Geology—a mistake which actually arrested for full seven years all pro- 
eress in the analysis of the older portions of the great Paleozoic System) been placed 
in a false relation to the Upper Cambrian (or Upper Bala) group. At a later period 
(1852) I proved that the Caradoc group had also been misinterpreted; and I at length 
(as stated above) discovered, with Professor M‘Coy, the true Silurian base. 
But apart from any discussion on this latter point, was the Silurian scheme of nomen- 
clature to stand good when the sectional groups on which it rested were struck from 
under it? Were geologists (British or Foreign) who had adopted the nomenclature on 
