THE IGNEOUS ROCKS OF THE BEREHAVEN DISTRICT. 157 
but that appearance is hard to be accounted for, as there is a num¬ 
ber of ashy-looking dykes branching from it to the south-east and 
north-west. There is also a dyke to be found farther east along 
the coast; but it is not traceable all the way, on account of the 
drift, though it seems most likely to have had its origin at this spot, 
as also all the dykes at or near Crow Head. This has all the ap¬ 
pearance of having been the vent of a small submarine volcano, as 
all the dykes which seem to be connected with it are of a very 
flaky nature, and such as one could imagine a volcanic ashy mud 
to become, on being consolidated. The slate underlying seems to be 
altered for the space of two or three feet. 
There are also a few seemingly contemporaneous traps at Drum- 
sharra Point, about 500 yards west of Pulleen Harbour, running 
about two feet thick; they do not seem to be very extensive, as 
they are not to be remarked anywhere else. One of them is a fel- 
stone porphyry, very like syenite in appearance; the other is very 
like a serpentine. They are close on the junction of the Old Red 
and Yellow Sandstone. There is also a felstone dyke to be found 
on the road leading from Dunboy to Pulleen, and another in Dun- 
boy Wood; they are felstone, and lie in the direction of the bedding; 
but the beds on either side are slightly altered. These are the only 
felstone dykes that were found in the Old Red Sandstone forma¬ 
tion. 
YELLOW SANDSTONE. 
The Yellow Sandstone in this district is not strongly developed, 
being only 700 or 800 feet thick; the principal igneous feature is 
a contemporaneous felstone, about 30 feet thick, traceable. from 
the coast about 500 yards west of Drumsharra Point to the coast 
near Cahirmore, where the Yellow Sandstone disappears in the 
sea. It is to be traced all the way, with the exception of a few 
small breaks. It is a bluish felstone porphyry, with white felspar 
crystals very widely disseminated through the mass. It is displaced 
by two faults. There are also two or three small beds of felstone 
near Drumsharra Point, and one hornblende dyke; but none of 
them are of much consequence. On coming to Cahirmore you find 
a number of small greenstone dykes, which make their appearance 
there; and a roundish mass of trappean breccia, which seems to be 
contemporaneous, to which reference will be made at a future period. 
