1848.] _ SEDGWICK ON THE SKIDDAW SLATE. 221 
fect, it is more nearly perfect than it was before the discovery of 
organic remains in the Skiddaw slate. 
I will not detain the Society with any account of a second excursion 
also made by Mr. J. Ruthven, under my direction, during which he 
found graptolites and other traces of fossils in localities where I should 
hardly have expected them. During this excursion he examined the 
lower arenaceous and slaty beds as they descended into the metamor- 
phic group. In these he found no fossils of any species, though among 
the arenaceous beds impressions of encrinites and shells might have 
been preserved, had such ever existed. 
§ 3. Concluding Remarks.—Nomenclature, §c. 
1. I believe that the fossils above described belong to the oldest 
fossil group of the British Isles; nor does it appear that any older 
fossil group has been found in America, Norway, or any other country 
yet examined. 
2. Does this group mark the descending limit of organic life? My 
belief is that it does nearly mark the limit. This is no new opinion, 
as I have often stated my conviction that the traces of organic life 
disappear in the descending sections, independently of their oblitera- 
tion from metamorphic action or mineral change. ‘This may be called 
an hypothesis, and I am willing that it should pass as such, and that 
it should be withdrawn when it is disproved. But what is the 
Huttonian view (viz that there is no descending limit of organic 
life) but another form of hypothesis? Moreover it is an hypothesis 
not suggested by fact, but by some supposed analogy between geo- 
logical and astronomical cycles. And again, this hypothesis appears 
to me opposed to physical evidence derived from considerations of 
temperature and of the figure of the earth. 
3. The base of the Cumberland series is more perfect and symme- 
trical than that of Wales, which has no zoological or physical true 
base-line. On a review of the whole case, I conclude that the Lingula 
beds (and those beds below them near the Merioneth anticlinal) are 
all above the greater part of the Skiddaw slate. 
4. By what names shall we define the great groups above noticed ? 
The Skiddaw group cannot be correctly coloured as one with the 
overlying slate and porphyry group, and lose its name. Physical 
development opposes this view, and organic remains do not confirm 
it. But it is a matter perhaps of indifference by what name (such 
as Skiddaw group, Taconic group, protozoic group) we may hereafter 
please to designate it. 
5. If we are to pay any regard to physical development, we can- 
not regard the vast group of slate and porphyry (No. 3) as only a 
portion of the group of Coniston (No. 4). It is the equivalent of the 
great Cambrian slate group, and is out of comparison the most remark- 
able physical group in the British Isles; and I will venture to assert 
that no man can describe the older rocks of South Britain without 
giving this group a prominent place. Its true name may be either 
the great Cumbrian or Cambrian slate group. 
6. Allthe higher rocks (up to the old red conglomerates) are parts 
