110 Cotu—The Rhyolites of the County of Antrim ; with a Note on Bauxite. 
bare by the action of a little stream, which has here cut through the basalt flows. 
At present only a few blocks can be found in the stream-bank, and these are not 
obviously in situ: but their characters distinguish them from the other rhyolites 
to the north and the south-east. The rock of Kirkinriola is a pale-bluish grey 
rhyolite, of the genuine ‘“trachytic” texture, minutely scoriaceous, and with 
porphyritic crystals of quartz and orthoclase. The microscope reveals a fair 
amount of darkened biotite; the quartz proves to be unusually idiomorphic ; and 
a delicate fluidal structure, only faintly seen in the field, is brought out by 
polarised light. The groundmass is lithoidal, and resembles that of the Tardree 
rock; but a number of minute pale brown-green wisps of mica are associated 
with the colourless rods. A microgranular structure appears between crossed 
nicols, independently of the orientation of the original crystallites; the granules 
are about ‘025 mm. in diameter, and are best studied on the thinnest edges of the 
section. Here it appears that they are merely flaky crystals of quartz and 
felspar, hidden away amid the mass of crystallites in the thickness of the slice ; 
the crystallites themselves, which mask their outlines in the body of the slide, are 
exceptionally minute and ill defined. 
It may be remembered that we were tempted to a different conclusion in 
accounting for the granulation in the rhyolite of Tardree. In such cases it is 
exceedingly difficult to ascertain whether a granule includes or is surrounded by 
a given group of crystallites. Where, however, the whole of a groundmass rich 
in crystallites appears as a mosaic between crossed nicols, it seems fair to conclude 
that the granules represent the final product of crystallisation, the settling down 
of what was for a time residual glass. Such does not appear to be the case at 
Kirkinriola. 
No conclusions can be drawn from the present exposures in the field as to the 
relations of the Kirkinriola rock to the adjacent basalts. 
VII.—Ba.iycLouGHAN. 
At Ballycloughan, translated as “ Quarrytown” on the Ordnance Map, in a 
fork between the roads from Broughshane and Ballymena, there is a little hill, on 
the crest of which rhyolite is exposed. A good quarry was worked here in former 
times for window-sills, &c.;* but there are now several respectable larch-trees 
growing in its floor. An old man whom I met remembered working in it, and told 
me, as one often hears in the county of Antrim, that coal had been obtained from 
it and burnt. Mr. Wm. Gray, F.G.S., has cleared up the mystery in this case; he 
tells me that a futile boring was put down near this spot by Scotch engineers in 
* Berger, op. ctt., Trans. Geol. Soc. London, vol. iii. (1816), p. 191. 
