169 
Geological Relations of the East of IrelancL 
Aston hill. The felspar is usually of a yellowish or greyish-white 
colour, unless when coloured greenish by mica, which mineral com- 
monly possesses a greenish hue, and approaches sometimes to chlo- 
rite on the one hand, or to hornblende on the other. The felspar 
and mica are sometimes so intimately incorporated as to constitute 
a mineral apparently homogeneous, much resembling some varieties 
of trap ; and in other places it sometimes verges toward clay slate 
in aspect and texture, as in West Aston hill and the eastern part of 
Rockstown. This granite sometimes acquires also a syenitic cha- 
racter, containing small crystals of hornblende, as in Carrigmore and 
Rockstown ; and in the western end of Dunganstown range, called 
Ballynameesdagh, it passes into true felspar porphyry, exhibiting a 
fine granular or compact ash-grey base of felspar, in which are 
inlaid small brilliant crystals of hornblende and glassy felspar. 
The granite of this district appears to support and to be imme- 
diately bounded by clay slate or quartz rock, but these rocks are 
again connected with others of an interesting character, the relations 
of which I shall now proceed to describe. 
§ 61. In the north-western confines, the strata of clay slate of 
Kilnamanna hill stand nearly on their edges, slightly inclined to- 
ward the south-east, the granite rock projecting at its foot and 
seeming to constitute its base. In Deputy’s Pass, the new line of road 
has been cut into this clay slate, and near the western entrance we 
perceive in it a bed about three fathoms wide, composed of granular 
felspar and mica in different states of incorporation ; thus bearing 
some analogy to the fundamental rock itself. 
In the north-eastern quarter, toward Dunganstown, the granite 
supports clay slate, which passes into a rock of a compound charac- 
ter, a base of clay slate in which are implanted angular pieces of 
quartz, hornstone, and crystals of felspar. This is succeeded by a 
Vol. V. 
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