HUGHES: ADAM SEDGWICK. 
267 
trying- to make these sections fit on to Murchison’s, which were 
utterly wrong-. 
Let us now consider what Murchison’s grouping was, and on 
what founded. We will go to Llandeilo to see what he meant by 
Llandeilo rocks. The beds to the west of Llandeilo were changed 
from Cambrian to Caradoc. The Cambrian and Llandeilo had to be 
turned the other way up. The Caradoc on the east of the valley 
was changed to Llandovery. 
This, however, was not so serious when we consider what was 
then meant by Caradoc which is quite clear from the description of it 
in the Silurian system and the fossils said to characterise it. See 
Sil. Syst., pis. 19, 20, 21, from which it will be seen that it included 
part of the Upper and part of the Lower Silurian. Thirteen years 
later, Sedgwick cleared this up in his paper on a proposed separation 
of the so-called Caradoc Sandstone into two distinct groups, 1, May 
Hill Sandstone, and 2, Caradoc Sandstone. So Murchison had not 
got Llandeilo or Caradoc right in his typical sections. 
It would not be profitable to try to pick holes in such a fine 
production as the Silurian system, where the labours of Lewis, of 
Agmestry, and of Williams, of Llandovery, and of the author are 
so skilfully worked in, and the beautiful illustrations of which 
make it a classic work never to be set aside as useless. 
But a question has to be answered in common justice. 
Two prominent geologists had put forward two different and 
contradictory schemes, before 1839. Which of the two was right 
in 1839 ? I submit without hesitation that Sedgwick was right in 
1839, and go further, I say that Sedgwick’s is still the classification 
most true to nature. 
If you look at Murchison’s later works, or at the publications of 
the Survey, which were issued under his direction, you will find 
that the great stratigraphical errors mentioned above have been 
corrected. But how ? Was it by acknowledging that he had mis- 
understood a local anticlinal bringing up some of Sedgwick’s Lower 
Bala, and had drawn a continuous ascending section across it; that 
he had missed the true break at the base of the Silurian, and grouped 
