84 CoLte—The Rhyolites of the County of Antrim ; with a Note on Bauxite. 
is so marked a feature of the decomposed rhyolite along the junction of its lower 
surface and the chalk. This clay breaks up along small close-set jomts, which 
may be those of the original glassy selvage of the rhyolite. On washing it for 
some time in water, numerous small angular lumps remain, of more resisting 
character; these prove to be cores of altered rhyolite which have held out against 
complete decay. A few microscopic fragments of reddened flint also occur, which 
have become embedded from the associated gravels. The finer portion of the 
residue, after washing off the mud, shows tiny lumps, probably of the original 
groundmass, altering into clay, and fresh flakes of orthoclastic and plagioclastic 
felspars, which are similar to those in the massive rhyolite. For comparison, 
pieces of the rhyolite were powdered to a similar degree of fineness. But the 
decomposed rock in one point differs markedly from the unaltered rhyolite. It 
abounds in minute prisms and granules, with a high refractive index, the 
measurable angles and extinctions of which prove them to be epidote. This 
mineral is clearly, as at Tardree, an accompaniment of the decomposition of 
the rhyolite. 
Thus we have, in about a vertical metre of the section, proof that the rhyolite, 
when oozing in among the gravels, encountered the pre-existing basalt also, and 
carried off at least one lump of it as a record. 
I think, then, that the relative ages of the rhyolite and the basalt at Temple- 
patrick may be considered as well established. The third division of Mr. M‘Henry’s 
argument, as I have summarised it above, merely shows that the rhyolites are 
older than the period of rest marked by the pisolitic iron-ores of Co. Antrim. 
Denudation might have reached down through the Lower Basalts to pre-existing 
rhyolitic material, and so might have produced the conglomerates of Ballypalady 
and the Libbert mine. So far as I am aware, the fact that the rhyolites of the 
county of Antrim are younger than the Lower Basalts is nowhere demonstrated 
except in the difficult sections at Templepatrick. 
It has been recorded, as we have already seen, that the rhyolite of 
Templepatrick is “‘ pierced by younger basic dykes.” This statement, however, 
possibly refers to the Tardree area. None of the dykes at Templepatrick, so far 
as I can observe, are seen in contact with the rhyolite. 
IIJ.—Carnearny, TARDREE, AND BarnIsH. 
In a recent paper * I have dealt with the general features of this extremely 
interesting area, and have urged that the dome of Tardree Mountain represents a 
voleanic core, from which true lavas flowed, forming the plateaus to south and 
north. This same view was put forward by von Lasaulx,t who arrived at it after 
* “ The Volcano of Tardree, Co. Antrim,” Geol. Mag., 1895, p. 303. _‘f ‘‘ Aus Irland”’ (1878), p. 167. 
