Ixxxiv INTRODUCTION. 
generally dark grey; more rarely of a reddish tinge; sometimes much penetrated by 
quartz veins; does not effervesce with acids; alternates with coarser gritty bands, which 
are, however, quite subordinate; is of very great thickness, forming the larger mass of 
Skiddaw and Saddleback, &c.; so far as is yet known, does not contain a trace of fossils, 
either vegetable or animal; presents the closest analogies with the rocks of the Longmynd; 
but as a type is perhaps more perfect than those rocks; inasmuch as it has a mineral, though 
not a palzontological, base. 
(8) Next in ascending order is a great group, occupying the high mountains between 
Keswick and Buttermere, in many parts of which the gritty bands begin to predominate. 
Its more slaty bands are, in structure, analogous to the slates of the preceding group. So 
far as it is yet known it is without a trace of fossils. Some parts of it, if exposed to 
metamorphic action, would pass into quartz rock. 
(4) Lastly, comes a higher group, also of great thickness; obscurely separated from 
the preceding (No. 3); and overlaid, in some places I believe discordantly, by the trappean 
conglomerates, chloritic slates, &c., which form the great central division of the older 
Cumbrian Series. In this fourth group are found, occasionally, more earthy dark-coloured 
slates, which contain some rare examples of Fucoids and Graptolites. It also contains 
traces of carbonaceous matter; which seems to have been partly sublimated into certain 
veins of the green slate and porphyry, and to have contributed to the formation of the black- 
lead mines of Borrowdale. 
I have never examined the Skiddaw Slates since 1824; but my opponent in nomen- 
clature has not examined them at all. And when he pronounces the whole collective 
group to be Silurian, from the existence of some rare Graptolites in the highest subgroup, he 
not only deserts the principles of sound nomenclature, but he mistakes, I think, his own 
position as an original observer among the older rocks of England. Here, as he had 
done before in Wales, he strives to clench the nomenclature before he has learnt, by a 
study in the field, to comprehend the characters of the physical groups. Till this is done, 
it is idle to discuss points of nomenclature while we are dealing with rocks of such 
antiquity as the Skiddaw Slate. 
Who can fix the date of the bottom rocks of the Longmynd? They have neither 
a mineral, nor a paleontological base to rest upon. Under these circumstances it is 
obviously impossible to decide whether the oldest Slates of the Longmynd be older or 
newer than the oldest Skiddaw Slates. The former have no base that I have ever seen or 
heard of. The latter are arrested by the Granite. Under these conditions it is a very safe 
assertion to make—“that the Skiddaw Slate does not exhibit beneath it any clear repre- 
sentative whatever of the Longmynd or bottom rocks.” Such a statement is a truism 
which tells us nothing. 
Should any one, after the above description of the facts, (and before they are met by 
some better interpretation of the older groups of Cumberland than I have given in the 
Tabular View), choose to call all the subgroups of the Skiddaw Slate, Silurian; I am 
