134 
JOURNAL OF THE GEOLOGICAL SOCIETY OF DUBLIN, 
5. The next in order is the Dingle district, into which I have 
entered already; and will only repeat that the band of brownstone 
at Sybil Head, below the fossils, is 3600 feet in thickness, not in¬ 
cluding the bottom beds, which are under the sea; and that between 
Clogher and Fintona, in the county of Tyrone, the brownstone rock 
is at least 7000 feet thick, without the lower beds also, which are 
not visible there. 
Those numbers go pretty far as an approximation to the thick¬ 
ness of the Old Red Sandstone of Scotland and England, with, how¬ 
ever, the important difference, that the British rocks are considered 
as Old Red Sandstone. The Irish equivalents—if equivalents they 
be—are undoubtedly Silurian. 
In the south of Ireland there are also other tracts of brown¬ 
stone, besides that in the vicinity of Dingle. They occur in some 
of the highest mountains in the country; for instance, Macgillicuddy’s 
Reeks, Tore, Mangerton, the Priest’s Leap, and other mountains 
in Kerry. In Cork are the Paps, the Boggra Mountains, Mount 
Hilary, Knockoura, and so on to the Knockmeldown and Cumme- 
ragh Mountains, in Tipperary and Waterford. 
The two localities, Dingle and Killery Harbour, are 200 miles 
asunder; and yet hand specimens of slate or grit, or specimens in 
the rock, abound in both, which for hardness, grain, or colour, 
could not be known asunder; and I may include with those, as 
having the same lithological character, Macgillicuddy’s Reeks, and 
the other mountains of Kerry, Cork, and Waterford, already enu¬ 
merated. In those lofty ranges, the association of the brownstone 
with green and gray grits, and gray, red, and purple slates, is of 
frequent occurrence, and requires some notice. In the grit beds, 
though they compose the chief volume of the mountain masses, no 
fossils have yet been discovered. 
Since fossils have become indicative of the age of groups of 
rocks, attention appears to have been drawn away from their litho¬ 
logical character. This, however, is not to be rejected; and it is 
particularly useful where no fossils are found. It is not easy to 
give a description in writing of a rock specimen, so as to be gene¬ 
rally understood; but I may say, that I would know even a hand 
specimen of the green grit of the Killarney Mountains, or the 
brownstone of Sybil Head, if I saw them or their equivalents at 
Londonderry, or anywhere else; and I think an experienced eye 
