742 STRATIGRAPHICAL GEOLOGY. — [Boox VI. 
to other geographical changes whereby the sediment was for a time 
prevented from spreading so far. 
Viewed as a whole, therefore, the Carboniferous Limestone series of the 
northern part of the British area contains the records of a long-continued 
but intermittent process of subsidence. The numerous coal-seams with 
their under-clays were undoubtedly surfaces of vegetation that grew in 
luxuriance on the wide marine mud-flats, and mark pauses in the 
subsidence. Perhaps we may infer the relative length of these pauses 
from the comparative thicknesses of the coal-seams. The overlying and 
intervening sandstones and shales indicate a renewal of the downward | 
movement, and the gradual infilling of the depressed area with sedi- 
ment, until the water once more shoaled, and the vegetation from 
adjacent swamps spread over the muddy flats as before. ‘I'he occasional 
limestones serve to mark epochs of more prolonged or more rapid sub- 
sidence, when marine life was enabled to flourish over the site of the 
submerged forests. But that the sea, even though tenanted in these 
northeru parts by a limestone-making fauna, was not so clear and well 
suited for the development of animal life during some of these submer- 
gences as it was further south, seems to be proved by the paucity and 
dwarfed forms of the fossils in the thin limestones, as well as by the 
admixture of clay in the stone. 
Ireland presents a development of Carboniferous rocks, which on the 
whole follows tolerably closely that of the sister island. In the northern — 
counties the lowest members are evidently a prolongation of the type of 
the Scottish Calciferous Sandstones. In the southern districts, how- 
ever, a very distinct and peculiar facies of Lower Carboniferous rocks is 
to Le remarked. Between the top of the Old Red Sandstone and the 
base of the Carboniferous Limestone there occurs in the county of Cork 
an enormous mass (fully 5000 feet) of black and dark-grey shales, impure 
limestones, and grey and green grits and true cleaved slates. To these 
rocks the name of Carboniferous Slate was given by Griffith. They 
contain numerous Carboniferous Limestone species of brachiopods, 
echinoderms, &c., as well as traces of land-plants in the grit bands. Great 
though their thickness is in Cork, they rapidly change their lithological 
character, and diminish in mass as they are traced away from that. 
district. In the almost incredibly short space of 15 miles, the whole of 
the 5000 feet of Carboniferous Slate of Bantry Bay seems to have 
disappeared, and at Kenmare the Old Red Sandstone is followed im- 
mediately and conformably by the Limestone with its underlying shale. 
Mr. Jukes held that the Carboniferous Slate is the equivalent of part 
of the Devonian rocks of Devon and Cornwall. 
The Carboniferous Limestone swells out to a vast thickness, and 
covers a large part of Ireland. It attains a maximum in the west and 
south-west, where, according to Mr, Kinahan,} it consists in Limerick of the 
following subdivisions : Feet, 
aie Ah i vad _fBedded limestone : 7 ‘ . 240 
Upper (Burren) Limestone \Cherty pein ; j ; 20 
A Limestones and shales, é d - 1000 
Upper (Calp) Limestone Gh erty zone ‘ 40 
Lrenestella limestone, P ‘ . 1900 
Lower Limestone .4 Lower cherty zone ) ; : “ 20 
Lower shaly limestones ; : . 280 
Lower Limestone Shale . ; ‘ : ; ‘ 100 ° 
1 Geology of Ireland, p. 72: 3600 
