TRANSACTIONS OF THE SECTIONS. 47 
from their geological position and lithological character, have been hitherto classed 
with the Devonian or Old Red Sandstone. 
He commenced with those districts hitherto classed and coloured on his Geologi- 
cal Map as Old Red Sandstone, 
'_ The most northern of these districts extends from Lough Erne eastwards towards 
Pomeroy, and occupies a tract about ten miles wide from Omagh to Ballygawley ; 
it comprises about 300 square miles of the country. 
This district is bounded on the north by igneous and metamorphic rocks, and on 
the east, south and west, by strata belonging to the carboniferous limestone of Tyrone 
and Fermanagh. 
He had already mentioned, in his paper on the Carboniferous Series of Ireland, 
that in our northern counties, where the red or gray sandstones which form the base 
of the carboniferous series come in contact with the inferior brownish-red sandstone 
or conglomerate, that the strata in every case show a sedimentary unconformability. 
The district in question, when viewed from the limestone country on any side, pre- 
sents a hilly character ; this is particularly the case along its south-eastern boundary, 
where it rises up from the carboniferous valley of Clogher at a steep angle, forming 
a range of hills which vary in height from 800 to 1000 feet. The strata dip from 
the valley towards the hills, so that the base of the series appears on the outer edge, 
The lower beds in the valley of Clogher, where they are visible at the unconfor- 
mable contact with the carboniferous sandstone, consist of a vast accumulation of 
beds of conglomerate alternating with beds of brownish-red micaceous sandstone, 
and rarely with red shale. The conglomerate is usually composed of imperfectly 
rounded masses of brown clay porphyry, varying in size from one inch to two feet in 
diameter, together with rolled masses of very compact greenish sandstone or quartzite, 
together with a green matter, probably chloritic earth, imbedded in a brown earthy 
porphyritic cement, composed of a base of brown earthy matter studded with crystals 
of white felspar more or less perfect. 
Near Cecil demesne, four miles north-east of Clogher, this conglomerate, in very 
thick masses, alternates with a brownish-red, apparently concretionary rock, com- 
sed of irregular sphericles of soft earthy matter, with much white mica arranged 
in laminz, so as to be only visible when split in the direction of the strike; when 
examined with a lens, the cross fracture presents a porous structure, and it is re- 
“ago that in no instance were any of the sphericles broken across in fracturing 
e rock. 
No pebbles or fragments of quartz were observed either in the porphyritic conglo- 
merate or in these finer beds, but the latter usually contains fragments of a very fine- 
grained brown slate, more or less rounded at the edges. 
In some localities, where these finer beds are wanting, the dip and strike of the 
conglomerate can rarely be determined except by observing the parallel position of 
bead smaller flattened porphyritic pebbles, and occasionally the finer sedimentary 
yers. 
On the large scale, therefore, this trappean conglomerate, which in many of its 
characters resembles the trappean ash beds of Sir H. Dela Beche, may be said to be 
arranged in beds, but on the small it bears a resemblance to compact gravel. In 
fact, in many cases where it appears at the surface on banks of rivers and streams, 
it cannot be distinguished from ordinary diluvial gravel except by its superior hardness. 
Quartz pebbles very rarely occur in this rock, a circumstance that seems to distin- 
guish these conglomerates from most others. 
: Ascending in the series, the conglomerate beds gradually diminish in number and 
_ thickness, and give place to the finer variety, which now assumes the character of an 
ordinary reddish-brown sandstone. the mica still prevails, and fragments of fine 
brown slate are frequently abundant. As the beds accumulate, reddish-brown shale 
_ appears alternating with the sandstone ; still ascending, the conglomerate disappears, 
_and the shale increases until, in the neighbourhood of Fintona and Dromore, the 
‘shale predominates. From the south-east. boundary of the district, as far as Dro- 
more, the strata dip north-west, but here is a synclinal axis and the dip is reversed, 

_ and consequently in proceeding from that place north-westward we are descending 
in the series, and approaching Dooish mountain we meet with a porphyritic conglo- 
_ Merate, dipping at a steep angle towards the southward, closely resembling that at 
_ the east border of the district already described. 
