220 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Feb. 2, 
4 
traces of organic remains in this group which I could quote with any 
confidence ; but I did (during 1822, when I was first employed on 
this eroup) find several traces of carbon, which have often suggested 
the idea that they must have been derived from some obscure forms of 
vegetable life, such as fucoids. 
In some letters on the Lake district, written about six year’s since, 
I mentioned the plumbago found among the slags of our iron-fur- 
naces, and also on the sides of trap dykes traversing the coal strata. 
Of such appearances, I added, that we could give an intelligible ac- 
count; and though I did not venture to account for the sublimation 
of the carbon found im the plumbago mines of Borrowdale, I 
suggested the possibility of its bemg derived from the Skiddaw slate, 
which I believed to contain, here and there, a small proportion of 
carbon. I mention this to show that the idea of vegetable matter 
existing durmg the period of the Skiddaw slate was not a new 
thought. Durimg the last summer my own engagements prevented 
me from undertaking the re-examination of the Skiddaw slate ; but 
I examined my old note-book of 1822, and gave a line of march to 
Mr. John Ruthven of Kendal, requesting him to examine all the 
most promising localities ; devoting his best efforts to the detection of 
any traces of organic life, vegetable or animal, however obscure. 
The result of his labours, continued with untired zeal for several 
weeks, was the discovery of two species of graptolites and two genera 
of fucoids in the Skiddaw slate. The accompanying catalogue by 
Mr. M‘Coy contains a description of the species, which are now on 
the table of the Society, with a reference to the localities, and is 
intended to form an appendix to this paper*. 
No fossil shells and no other undoubted organic structures were 
found in the Skiddaw slate; and it deserves remark, that in the 
greater part of this slate the beds do not effervesce with acids. By 
this test we can generally separate the Skiddaw slate from the dark- 
coloured slates of the groups above the Coniston limestone ; a fact 
first noticed nearly thirty years since by Mr. J. Otley of Keswick, but 
in no connexion with any speculation on the absence or presence of 
fossil shells. Here then we have taken away a part of the difficulty, 
already alluded to, in the comparative arrangement of the older rocks 
of Wales and Cumberland. The great slate and porphyry group 
(No. 3), so far as we know, does not contain fossils; but it does 
contain much calcareous matter, and it does overlie a group with 
fossils. It is therefore not only possible, but highly probable, that 
under conditions more favourable to the development of organic life, 
other contemporaneous deposits (such as the older Cambrian slates) 
may exist with abundance of fossils. Hence, though the comparison 
between the older groups of Wales and Cumberland is not yet per- 
* The fossils are rather obscure, but of their organic nature there can be no 
doubt. Some of them were first considered as Annelides: but the grapto- 
lites, are well defined. So far as regards my immediate object, the specific 
character of the fossils is a matter of indifference—my main object being 
at present only to show that the Skiddaw slate is not below the limits of 
organic life; and, hence, that the great group, No. 3, must belong to an organic 
period. 
eo 
