264 
HUGHES : ADAM SEDGWICK. 
same horizon as the lowest of Wales. He further suggested the 
mode of connecting Murchison’s work and his own, of course he 
assumed that Murchison’s sections were correct. 
Here we find the terms Cambrian and Silurian fully recognised, 
and we need not refer to the mere question of nomenclature again. 
We have only to consider as we go on and get further evidence to 
what it was that each author applied his own term, and where they 
came in collision as to the grouping of the rocks, whose classification 
was true to nature. 
Now what did Sedgwick mean by Cambrian previous to 1839 ? 
Following up his investigations in N. Wales he offered in 1838 a 
further tentative grouping which is very nearly that which must be 
adopted now. It is as follows in descending order : — 
WALES. LAKE DISTRICT. 
Refers to Murchison’s Silurian , as des- Upper Division with no marked un- 
cribed in his papers and “forth- conformity at the base. Flags, 
coming work.” quartzose, greywacke, coarse 
slates with imperfect clevage., 
III. UPPER CAMBRIAN. 
From the base of the Grits which 
= Caradoc of Murchison to Bala 
Limestone. [We shall see that 
Murchison’s then called Caradoc 
was tbe May Hill S., not what 
Murchison and the Survey after- 
wards called Caradoc]. 
Lower part, Slates based on Calc 
Slates passing into Limestone 
(Coniston Limestone). [This part 
is a little obscure in consequence 
of his not having yet made out 
the true position of the Ireleth 
Slates]. 
II. LOWER CAMBRIAN. 
The Volcanic Series of Snowdon, Glide Slates, compact felspar, felspar por- 
Fawr., &c. phyry, and brecciated porphyries. 
I. [He does not yet give a name to these.] 
The older Slates and Quartzites of Nothing to show that this group is 
Anglesea and Carnarvonshire. analogous to that of Skiddaw. 
He quotes Murchison’s Llandeilo Flagstones and Caradoc. 
He did not add much to the above in his paper read before the 
Geological Society, in 1841, but now the “ Silurian system” had been 
published, and the difficulty of making his work agree with Mur- 
chison’s sections was evidently increasing. 
In June, 1843, he offered some further notes on N. Wales, 
and still finding no organic remains in the oldest and generally most 
highly metamorphosed rocks, did not very clearly define their age, 
but placed them correctly at the base of the whole series. He now 
