273 
Geological Relations of the East of Ireland. 
phyry, and the contained crystals being of glassy felspar. This 
compound passes into claystone, which sometimes becomes so 
charged with iron, as to pass into iron claystone, both red and 
black, which are either compact or porphyritic. The trap con- 
glomerate consists of an intermixed base of trap and limestone, 
cementing fragments of both the same kinds of stone ; and in the 
limestone of this conglomerate I have observed organic remains. 
§ 174. In crossing the valley from Castleguard toward the 
south, we travel over continuous strata of bluish grey limestone for 
nearly two miles, which are succeeded for about one mile by red 
trap, arranged in massy strata four and five feet thick, both rocks 
preserving the same dip of 10°. This bed of trap probably under- 
lies the limestone bed of Mount Catharine, which seems in its 
outgoing to form the north-eastern and eastern base of the trap 
range which extends through Knock Rua, Knock Dirk, and Kil- 
teely hills; (see Plate 7. No. 5.) But, in the vale, about one mile 
to the north-east of Mount Catharine are the two slight eminences 
of Tullogh and Cross : which constitute in their northern extension 
the low elevations called Brackheel and Coolanapish hills, and the 
whole form together one great bed of trap, principally composed of 
porphyry of various shades of red, brown, grey, and green, disposed 
in thick massy strata. To the eastward of Cross is limestone again, 
and beyond this, still more east, Knock Hourach, which also is 
composed, I am informed, of trap, resting on limestone : and this I 
apprehend to be the eastern limit of the trap beds. 
§ 175. Limestone rock is to be seen in several places low down 
on the eastern flank of the trap range of Knock Rua, Knock Dirk, 
and Kilteely, and it is evidently the basis of this range which appears 
to constitute one great prominent bed. The same rock is visible 
also on the western flank, occupying the hollow which separates this 
Vol. V. 2 m 
