1388 THE Rev. MAXWELL H. CLOSE, 
At Portrane there is, on the shore, a small, but very noticeable, 
exposure of this formation. ‘The beds are sometimes much con- 
torted, but their general dip on the shore is towardsS. of E, The 
rocks consist of slates and shales containing graptolites and trilo- 
bites, with some grits and, more especially, highly fossiliferous beds 
of limestone; all the fossils being of Bala or Caradocage. There are 
also several interstratified beds of trappean ash, evidently con- 
nected with the contemporaneous felstone porphyry close by on 
the W. and 8. There is, in some places, a well defined cleavage 
whose planes dip about 8. 60° E. at 40°, 
Lambay Island is 2% miles off Portrane. It is principally 
composed of felstone porphyry with various small masses of 
Lower Silurian stratified rock, some probably caught up in the 
felstone. The slates of some of these yield graptolites, At Kiln 
Point, on the shore near the S.H. angle of the Island, there is a 
mass of thin beds of limestone which contain Bala fossils; they 
have thin earthy shales between them. The felstone has sent 
veins and strings into the lowest bed of the limestone; but it 
has not had much altering effect thereon. The geological interest 
of this island is increased by the occurrence, near its N.W. point, 
of a remnant sheet of Old Red Sandstone (?) not more than 50 
feet thick. This consists of sandstones above, and a conglomerate 
below. It extends along the 8. side of Broad Bay for a length of 
nearly one furlong; the beds dipping N. at from 60° to 30°. 
The base of the conglomerate is well seen; it lies unconformably 
on the Lower Silurian ash and slates, which, at.this place dip S. 
at about 50°, and must be now inverted. The N. part of this 
remnant sheet is cut off by an EH. and W. fault. 
The black slates which occupy the low south-eastern part of 
Treland’s Eye, and which apparently rest unconformably on the 
Cambrian rocks, most probably belong to this formation. 
At afew miles southward of Dublin, the Lower Silurian sets 
in as the surface formation; it extends thence to Waterford 
Harbour, except that it is interrupted by the Cambrian and 
oranitic exposures, 
The rocks of this Lower Silurian area within the district with 
which we are now concerned, are unfossiliferous ; but in Wicklow, 
at Sheveroe, near Rathdrum, and in the Co. Wexford, they have 
yielded various fossils of Bala or Caradoc type. The small ex- 
posure of this formation at the Chair of Kildare, twenty-four miles 
, — 
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