Reviews—Geological Survey of Ireland, 239 
by drifts, to the south of the Old Red Sandstone, near the northern 
margin and to the west of it in the Slievefelim district. 
The overlying Lower Limestone consists in the lower portions of 
earthy limestone, in parts shaly, passing up into blue and grey lime- 
stone, much purer in quality than the lower strata, containing some 
chert, and being in certain places dolomitic. 
It forms a strip 2 to 14 mile wide (the northern limb of a syncline), 
overlying the Lower Limestone Shales in the north of the map area, 
forms an anticline over 2 miles broad in the south-eastern district, and 
occupies large areas on the east and west sides of the district. 
The Middle and Upper Limestones are undistinguishable in this 
district. A band of cherty beds from 20 feet to 150 feet in thickness 
has been taken as characterising the incoming of the upper series, 
which includes the Middle and Upper Limestones. Large con- 
temporaneous masses of igneous origin frequently come in just above the 
cherty beds. Over these cherty beds or, where present, over the igneous 
rocks are dark-blue, sometimes black, fetid, argillaceous limestones, 
that generally have thin shale partings between the beds; these are 
in some places succeeded, as we ascend, by another group of igneous 
rocks, and these again by blue compact limestone. The Upper and 
Middle Limestones, including the associated trappean rocks, are, 
calculated to be about 2,000 feet thick. They occupy a great 
synclinal basin with minor anticlines in the centre of the area. 
- In the south-east corner of the area occur two series of beds, which 
were originally regarded as Coal-measures, but which correspond in 
stratigraphical position and approximately in age to the subdivisions 
that have been correlated elsewhere in Ireland with the English 
Yoredale Shale and Millstone Grit respectively and are now mapped 
as such. 
Within the limits of the present sheet occur three bees areas of 
igneous rocks, mainly of volcanic origin, and some seven smaller 
outlying areas. Viewed in association with similar rocks which. 
appear throughout an area extending some twenty miles to the 
south-eastward, they render this region, in the words of Sir A. Geikie, 
“one of the most varied and complete of all the Carboniferous volcanic 
districts of Britain.” 
The igneous rocks described are Volcanic Tuff and Ash, Basalt and 
Dolerite and Trachytic Rocks (Orthophyre [ Orthoclase porphyry | 
type). It has been generally held that the basaltic ‘oles of Carrigo- 
gunnel and Boughilbreaga are contemporaneous and ‘ interbedded ’ 
with the tuffs of these localities. Mr. Kilroe cites evidence in favour 
of the view that they are intrusive. If, as is possible, the sills are 
of the period to which the great basic mass south of Ballybrood 
belongs, they would be more recent than the Millstone Grit, but how 
much more recent there is no evidence to show. 
» The Glacial Drifts. While most abundantly developed on the 
lower ground, the glacial deposits are found overlying the solid rocks 
in every part of the district. 
‘ Unstratitied boulder-clay, the direct product of the ice- -sheet, con- 
stitutes the most prevalent type of. glacial drift, but there are 
extensive masses of stratified drift consisting of sand and gravel 
assorted and deposited by water. ‘The two varieties of Boulder-clay- 
