Dingle and Glengariff Grits. 227 
deposit of the Welsh lake” basin; and on looking at a Geolo- 
gical map of Great Britain and Ireland, it is evident that the rocks 
which form the subject of this paper are part of those accumulated 
in the north-west portion of this basin. 
Let us now return to the Dingle and Glengariff rocks. Although 
Griffith classed them with the Silurians, while Jukes would class 
them with the Old Red Sandstone, yet both would seem to agree* 
that the Dingle Beds are equivalents of the older portion of the 
Glengarift Grits, or, as Griffith affirmed before the Society, the 
- visible Glengariff Grits as a niass are higher up than the visible 
Dingle Beds as a mass. 
These observers also agreed that while the Dingle Beds are 
capped unconformably by the “Old Red Sandstone,”t the Glen- 
gariff Grits extend upwards conformably into that group, and 
thence up to the Coal Measures. 
The Dingie Beds at the westward of the Dingle Promontory, 
as indicated in the accompanying diagrammatic section, are at least 
10,000 feet thick, but eastward higher beds come in, The Glen- 
gariff Grits south of Dingle Bay, as far as seen, are of somewhat 
similar thickness; though they are doubtless complete, yet the 
lower 3,000 or 4,000 feet, which rest on the Marine Silurians, are 
not exposed. 
It is evident that an early E. and W. fault, having a down-throw 
to the northward, extends along the valley of Dingle Bay; and 
that it has a considerable throw, of at least 5,000 feet, is proved by 
the position of the Coal Measures near Killorglin, which probably 
are in juxtaposition with the Glengariff Grits that underlie the 
tract of “ Old Red Sandstone” on the south of the fault. 
The place in about which this fault (Dingle Bay fault) occurs 
is indicated in the diagram. There are also other lines of fault 
that extend from the Lakes of Killarney to Dingle Bay; but in 
the diagram, these and others that occur farther southward, as 
also the undulations and minor breaks, are not represented ; the 
horizontal distances, however, are correct—that is, the distance 
from the centre of Dingle Bay to the centre of Kenmare river (24 
* Memoir Geo. Survey, Ex-sheet 182, fn. page 10. 
{ Here and elsewhere in this paper the Upper or Carboniferous Old Red Sandstone will 
be mentioned under the title of ‘‘Old Red Sandstone,” while the Lower will be called 
either “‘Glengariff Grits” or ‘“‘ Dingle Beds.” 
Scien. Proc., R.D.S. Vou. 11., Pt. 11. R 
