218 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Feb. 2, 
therefore assist the memory and help the reader in comprehending 
the facts here stated, and the inferences which seem to follow from 
them. 
§ 2. Classification of the preceding groups, &c. 
I would first remark that all the preceding groups are true physical 
groups; and I may venture to affirm, that any one examining the 
region in detail would imevitably be led into some arrangement, at 
least, nearly resembling that given above, and without any reference 
to the consideration of organic remains. Good physical groups are 
the foundations of all geology; and are out of all comparison the 
most remarkable monuments of the past physical history of our globe, 
so far as it is made out in any separate physical region. 
Organic remains are, in the first instance, but accessories to the 
information conveyed by good sections. But when the successive 
groups of organic remains are once established, in coordination with 
actual sections, they then tell us of successive conditions of organic 
life, which were (as we know by experience, and might perhaps have 
conjecturally anticipated) of far wider geographical extent than 
the local physical movements which produced the successive groups 
of deposits. Hence it follows, that in comparimg remote deposits, 
organic remains become no longer the secondary but the primary 
terms of comparison. It was plain, at first sight, that the organic 
remains of the Coniston limestone were entirely different from those of © 
the highest group of the slate series (No. 7). This I saw in 1822. 
But what was their general place in the old British series? The 
rocks of Devonshire were considered by all geologists of that day of 
extreme antiquity, and were of much older aspect than the arenaceous 
slates and flagstones of Westmoreland ; but they contained a series of 
fossils with several species identical with those of the mountain lime- 
stone; whereas the fossils of Coniston and Kirkby Moor had not, so 
far as was known, one species common to the mountain limestone. 
Here was the first great difficulty which I encountered so far back as 
1822, and which was not solved before 1838. After examining a por- 
tion of North Wales in 1831-1832, I felt all but certain that the great 
mass of slates and porphyries of Snowdonia were coeval with the green 
slates and porphyries of Cumberland (group No. 3) ; and this opinion 
I still retam. At that time my Cumberland and Westmoreland 
fossils were inaccessible: but on the best evidence I then possessed I 
ventured to conclude, that the green slate and porphyries were the 
equivalents of the Snowdonian series—that the Coniston limestone re- 
presented the Bala limestone-—that the contorted slates of South Wales 
were the equivalents of the Ireleth slates (group No. 6)—-lastly, that 
the highest group (No. 7) represented the Silurian system im an imper-, 
fect and degenerate form. So soon as I had unpacked my fossils in 
a subsequent year, I revoked this opinion. The Coniston limestone 
appeared not to represent the Bala limestone, but a higher group 
(Liansaintffraid limestone) ; and no traces of Lower Silurian species 
were found in the higher groups (Nos. 5, 6 and 7). Mr. D. Sharpe 
soon afterwards published (with many excellent and new details) a 
nearly similar classification. We now know the true coordination of 
