98 
JOURNAL OF THE GEOLOGICAL SOCIETY OF DUBLIN. 
but where the bedding is at all discernible, it dips southward from 
35° to 40°; where the cleavage prevails, its inclination and strike 
coincide with those of the beds. Fossils are sparingly scattered 
through these limestones, and consist chiefly of crinoid fragments. 
As we proceed westward, dark gray chert sometimes occurs in irre¬ 
gular and thin lumpy layers, but generally the rock is homogeneous 
in character. Below the beds just described are others which are 
finely crystalline, with numerous hard, irregular, semi-calcareous 
layers, weathering out like chert. These siliceous beds are well 
seen on the western shore of Dundag Bay, close to Muckross Abbey, 
the seat of Colonel Arthur Herbert; they also dip southward at 
60° to 70°, and may probably be about 200 feet in thickness. The 
same beds cross the entrance to Kilbeg Bay; and close to the Devil’s 
Island they are contorted in such a manner as to indicate the presence 
of a fault, which he named the Doo Lough fault. 
Immediately below these siliceous beds, light gray laminated 
limestones again occur, similar in character to those first described, 
and traceable along the shore of Mine Paddock Bay still farther to 
the west, dipping south at 40°, and presenting a thickness of about 
300 feet. 
At the northern extremity of Mine Paddock Bay a remarkable 
set of beds are now observed. These are best seen at the “Marble 
Quarries” west of the bay, and consist, first, of thin lenticular layers 
of white, pink, and greenish compact marble, with numerous irre¬ 
gular laminae of green and purple argillaceous shale, not calcareous. 
Second, light-gray compact marble, in very thin layers, with light 
green argillaceous shale partings, the average dip of all being south¬ 
wards at 30°, with a thickness of about 50 feet. These beds are 
totally devoid of fossils. Below these marble layers the limestone 
becomes gray and finely crystalline, with chert layers arranged 
closely together. As we descend in the series, the chert dies out; 
and along the shore east of the old copper mine the limestone becomes 
decidedly crystalline and fossiliferous, rather regularly bedded, and 
the chert occurs sparingly in nodules. About 500 feet west of the beds 
last described, the old copper mine occurs; it appears as occupying 
a break in the limestones, striking E. N. E. from the shore, where 
it is filled with decomposed iron pyrites. Fragments of copper 
pyrites lie scattered about, and many of these, when broken, exhibit 
strings of galena. West of the lode the limestones become thin- 
