170 
Mr. Weaver on the 
bed of greenstone, which is followed by a considerable bed of quartz 
rock graduating eastward into hornstone, and even into compact 
felspar. But the central and south-eastern parts of Dunganstown 
hill are wholly composed of greenstone, variously modified in as- 
pect. At the summit, it is more crystalline than in other parts, 
composed of distinct crystals of felspar with hornblende. But in 
general hornblende appears only in spots, or as colouring the felspar 
mass, which is partly compact and partly foliated, and in which 
are disseminated minute crystals of felspar. The grain varies from 
fine granular to compact, and the common character of the rock in 
the latter state is that of a base of a greyish green colour, with an 
uneven fracture and a tendency to conchoidal in the great, which 
contains disseminated minute crystals of glassy felspar. The range 
of these rocks is north-east and south-west. The trap is divided 
into strata from 12 to 18 inches thick, inclined at an angle of 80° 
toward the south-east. These strata exhibit a disposition toward 
columnar distinct concretions, each stratum being subdivided into 
rude irregular columns with four, five, and six sides, and the axes 
of these columns are parallel to the line of the dip. In the north- 
eastern part of this hill, the rock-approaches more to the nature of 
an ash-grey compact felspar, partly vesicular, the vesicles being 
mostly empty, or slightly coated with iron ochre., These trap 
rocks contain occasionally disseminated iron pyrites. 
The eastern and western portions of West Aston ridge are clay 
slate, with the same range and dip as in the adjoining country; and 
this rock extends to the Avonmore, nearly enclosing the granite ; and 
accordingly, in ascending this river by the eastern bank we meet 
with clay slate beyond the latter rock. It contains some thin beds 
of hornstone and felspar porphyry ; and to the north-west it rests 
upon a thick bed of greenstone, that incloses a bed of roofing slate, 
