240 
Mr. Weaver on the 
support the trap of the hill of Allen. We shall have occasion here- 
after, in the course of this paper, to return to the limestone of the 
Chair of Kildare, and to the trap of these hills. 
§ 138. The Slieve Bloom mountains (see Plate 6. No. 2. and 7. 
No. 3.) consist of a nucleus of clay slate surrounded by sandstone. 
Pure clay slate is found here, but it is also frequently of a quartzy 
nature, graduating into flinty slate, and sometimes it shews a 
tendency toward the character of fine grained greywacke. These 
rocks range nearly east and west, or between 20° south of east and 
15° north of west, dipping 70° toward the south. The sandstone 
appears to sweep round the clay slate nucleus, following the 
sinuosities, and curvatures formed by its surface, with a dip that 
conforms to the declivity. Quarries are formed all round the 
mountains, in some of which the strata are from one to three feet 
in thickness ; while in others excellent flags are raised from an inch 
to four or five inches thick, and seven and eight feet square. 
The sandstone of the Slieve Bloom hills seldom assumes the con- 
glomerate character, and, as seldom, acquires the deep red cast, so 
characteristic in general of that rock. It is commonly yellowish 
white, or grey, composed of granular particles of quartz, closely 
aggregated ; but it sometimes exhibits small porous interstices filled 
with yellow iron ochre. 
§. 139. Sandstone in mass, extends from hence considerably to 
the southward, beyond Roscrea and the Devil’s Bit mountain, often 
appearing in the form of conglomerate ; (see Plate 7. No. 3. and 4.) 
The Bilboa and Keeper mountains likewise are surrounded by a 
mantle of sandstone, except in a small portion on the north side, to 
the south and east of the village of Silvermines ; where, toward the 
foot of the hills, the clay slate nucleus comes immediately in 
contact with and supports the floetz limestone. The direction of 
jthe strata in this tract of clay slate appears to vary in different 
