156 
JOURNAL OF THE GEOLOGICAL SOCIETY OF DUBLIN. 
to have been poured out at two distinct periods, as, on going fur¬ 
ther west, a small bed of altered slate is found in it, about one foot 
thick in the largest place, dying out after going about forty feet to 
the east; and at about thirty feet below the surface, as seen by the 
coast section (Fig. 1), which at that place cuts right through the 
beds, showing a magnificent transverse section; it is then traceable 
to the north side of Dursey Head, where it disappears in the sea. 
The eruptive traps all spring from a large, irregular centre, with 
dykes running out on all sides,—some carry on for a good distance, 
but none of them are traceable for more than five hundred yards, 
while some do not exceed fifty, and generally end most abruptly. 
They seem to have been in action at a later period than the con¬ 
temporaneous traps, as many of the beds with which they have come 
into proximity are twisted and contorted to a great degree. It 
would seem to have been the great boiler (if I may so call it) for 
one of the subsequent volcanic eruptions which took place in this 
neighbourhood. They are, for the most part of the same nature as 
the contemporaneous trap, but do not seem to have any ashy por¬ 
tion in them. 
There is also a small greenstone dyke to the north of the Doo- 
neen Mine, which seems to belong to this period; also a few small 
dykes in the mountains, to the south-east of the Mine Yalley, which 
may be placed in the same classification. 
THE SOUTHERN DISTRICT. 
These traps (a pale, ashy-looking greenstone) have a most marked 
difference from all the others, and seem to have no connexion with 
them whatever. They range along the coast from Crow Head 
to about half-way to Cahirmore, generally running very small; 
the largest is not more than three feet thick, and most of them 
about one foot and a half, the small ones about nine inches; none 
of them seem to be contemporaneous; all nearly vertical, dipping 
to the north, and running in a direction for the most part E. 15 N.; 
they are not easily traced, on account of their small size, and the 
country being covered with drift and bog. They are to be seen 
to the best advantage on the north-west side of the Crow Head 
promontory. Going to the eastward toward Cahirmore, to the 
point to the east of Firkeel Bay, there is found a small oval mass 
of volcanic matter, of an ashy appearance. It seems to be contem¬ 
poraneous, having the same stratification as the surrounding slate; 
