100 
JOURNAL OF THE GEOLOGICAL SOCIETY OF DUBLIN.. 
On the north shore of Muckross, the limestones, though well ex¬ 
posed, do not present such clear sections as on the south; and at one 
inlet, to the east of the Carboniferous Slates of West Meadow Bay, 
a dyke-like mass of light brown crystalline dolomite, 6 to 8 feet 
thick, filled up an apparent fault in the limestone below the Car¬ 
boniferous Slates of West Meadow Bay, which dip S. and S. E. at 
from 25° to 40°. The upper Old Red beds appear on the south 
shore of the bay. 
UPPER OLD RED SANDSTONE.* 
The upper Old Red observed in Muckross Demesne occurs in a 
band of about 400 feet in thickness; it is well seen in the south 
shore of West Meadow Bay, where its general strike is W. S. W. It 
abuts against the east side of the Doo Lough fault, which, being an 
upcast to the S. W., shifts it for a considerable distance to the south¬ 
ward ; these beds are then traceable on the south shore of Doo Lough, 
from whence they continue westerly till they strike on Brickeen 
Island, where they are cut off by the fault previously noticed. They 
may be briefly described, in descending order, as consisting of:—1. 
Thick and thin quartzose grits. 2. Purple slates. 3. Greenish and 
gray shales, and slates with sandy slate beds, containing root-like 
impressions of plants. 4. Yellow grits and shales, with thin calca¬ 
reous layers. 5. Gray grit. And lastly, purple slates. 
Directly below the upper Old Red, just described, are a series of 
purple slates and grits, which preserve the same character for the 
thickness of 400 feet, when a mass of hard, irregularly bedded, light 
greenish-gray grits occur, quite free from purple slates. These form 
the cliffs from Ardnagluggen Point to the Gun Rock; calcareous 
bands occasionally appear through these beds. 
The eastern half of Brickeen Island, with the adjoining rocky 
islets to the north, is formed of purple slates and grits; but these 
are cut off by the Brickeen Island fault, and abut against the lower 
greenish-gray grits which form the western extremity of the island. 
To complete the description of the Carboniferous Limestones of 
* In order to avoid any controverted points in the classification, it is thought 
best to use the term “Old Red Sandstone,” instead of Devonian, throughout this paper. 
The beds, which are here called “ Upper Old Red Sandstone,” are believed to be those, 
more or less completely, which Dr. Griffith marks by a yellow band in part of this 
district, and denominates “Yellow Sandstone.” 
