126 
JOURNAL OF THE GEOLOGICAL SOCIETY OF DUBLIN. 
16. At Templetown, near Hook Point, the rock is well exposed 
all the way on the shore, and yet the resulting thickness appears 
small; but there are two faults in this section, by each of which 
there appears a downthrow to the south, the amount of which can¬ 
not even be guessed at. This makes the result, in this section, too 
little. On account of the rock being well exposed, this is one of 
the best typical sections I know, and in the upper part of it, at 
Porter’s Gate, the yellow sandstone of Mr. Griffith is particularly 
clear, and separated from the main body by a band of calcareous 
black shale, containing thin beds of gray limestone, both shale and 
limestone being full of the fossils of the mountain limestone. 
The general average of the thickness of the Old Red Sandstone, 
as measured in the foregoing sixteen sections, is 840 feet. Taking 
out six of the most doubtful, that is, Nos. 6, 12, 13, 14, 15, 16, in 
the Table, the average of the remaining ten sections is 910 feet. 
Four of the best of them, viz., Nos. 1, 2, 9. 11, give an average of 
1018 feet. In short, about 1000 feet may be considered as the 
thickness of this division. It will be at once apparent, that measure¬ 
ments of the thickness of this rock, in Ireland, fall very far short 
indeed, of the ideas of thickness derived from reading published 
accounts of the Old Red Sandstone of Great Britain. 
Plaving thus, as well as I could, pointed out marks for the iden¬ 
tification of this subdivision of the Carboniferous rocks, in the band 
of conglomerate at its base, its average thickness, and, above all, the 
unconformable position in which it lies on the supporting rocks,—I 
now come to consider the second part of my subject, that is, the 
relations of those older rocks among themselves. 
The Dingle peninsula is the key of the geology of the south of 
Ireland. From the extent of sea coast and of rocks laid bare, 
I know of no place where they can be studied with more advantage, 
and the fossils they contain afford proofs of their true place, if 
doubt or obscurity existed regarding them. In no other place 
are found such clear junctions, or such decided proofs that the 
Old Red Sandstone, and the rocks on which it rests, are of two 
different epochs in the earth’s history. I shall, therefore, enter on 
a short account of the Geology of that district. 
Besides the New Red Sandstone, and the Old Red Sandstone, 
we have in Ireland another Red Sandstone, or grit, which, I have 
reason to believe, has frequently been confounded with, or mistaken 
