110 
JOURNAL OF THE GEOLOGICAL SOCIETY OF DUBLIN. 
It appeared to him that in this district there was a better develop¬ 
ment of these, the lowest subdivision of the Old Red Sandstone, 
than he had observed elsewhere in the south of Ireland. 
Directly N. W. of Lough Gourach, in the Hag’s Glen, is a remark¬ 
able peak of rock called Stoompanaduff; and lower down the glen 
are the pyramidal masses called “ The Hag’s Teeth, Great and Little.” 
These are evidently what would be called Needles, if they occurred 
on a coast line, and have been formed by the denuding power of the 
drift sea. Here the purple grits and slates have a dip to the 
west, of 10° to 25°, and are traversed by joints running nearly N. 
and S., E. and W.; the action of sea-breakers on such strata caused 
the mass to wear away on the cross joint, leaving pinnacles such as 
we now see standing out from the face of the cliff. 
Descending from the summit of Carrantwohill on the south, to 
Lough Currachmore, which lies at the head of the northern spur 
of the Black Valley, a third natural section of the middle or purple 
part of the Old Red Sandstone is obtained. The summit of Carran¬ 
twohill is 3414 feet; Currachmore Lake, which is surrounded by 
these beds, is 1004 feet above the sea: hence the vertical section is 
2410 feet in thickness, increased, if measured at right angles to the 
beds, to about 4000 feet; by adding the thickness obtained by this sec¬ 
tion to that of the Hag’s Glen, a total amount of probably 5000 feet 
may be assumed as the thickness of the middle subdivision, or 
purple grits and slates of the Old Red Sandstone, in this locality. 
Allowing, therefore, 400 feet as the thickness of the upper Old Red 
or “ Yellow Sandstone” of Muckross, and, say, 5500 as that of the 
lowest subdivision, or the greenish-gray grit with conglomeritic 
layers of the upper Lake and the Black Valley—we have a total of 
10900 feet, as the observed thickness of the Old Red Sandstone for¬ 
mation of the Killarney district. 
Proceeding down Curraghmore Glen, along the N. E. base of 
Sugarloaf Mountain, the lower Old Red rocks are alone observed; 
but, on making the ascent of this mountain, which is 2449 feet in 
elevation, we soon pass into the middle purple grits and slates 
which form the main mass of the hill, lying in a kind of trough in 
the lower beds, but in every instance strictly conformable to them. 
The entire of the mountain ranges which now strike south by 
Lough Duff, the most westerly of the Black Valley Lakes, to the 
road leading to Lough Brinn, are composed of the middle purple 
