Mr. Weaver on the Geological Relations of the South of Ireland. 41 



The hill is composed of limestone, and the strata are curved from south to 

 north, but the crown of the arch is ruptured, the line of fracture being from 

 south-west to north-east, and the beds basset out on the opposite sides of the 

 rupture under an angle of 30°, in the western part of the hill dipping toward 

 the vale, and in the eastern from the yale. The strata in the eastern part of 

 the rupture present a bluff toward the valley, which is on a line with the bluff 

 of Knockeen limestone hill, distant a few miles on the east, while still further 

 east, on the same line, appears the trap bluff or precipice of Pallis Hill, im- 

 pending over Linfield. As viewed from the summit of Carrig Parsons, the 

 trap ranges are most prominent on the south-east near Pallis Hill; thence re- 

 ceding toward the south and west, through the Cahirconlish, Carrigfeoch, Bal- 

 lochbega, Ballinaguard, Knocknea, and Cahirnarry ranges ; while to the north- 

 west, and more insulated, rise the trap hills of Carrig O'Gunnel, adjacent to the 

 Shannon ; and to the west of north appears the insulated trap range of New- 

 castle, which, in its extension west, approaches within a short distance of the 

 artillery barracks at Limerick. In the series of such of these trap and por- 

 phyry rocks as have come under my view, I have not succeeded in finding 

 the stilbite, mesotype, and olivine, which Mr. Ainsworth states he had noticed. 



I shall here merely add a few remarks on the trap formation at Carrig 

 O'Gunnel, Knocknea, Cahirnarry, and the porphyry south of Lough Gur. 



The castle of Carrig O'Gunnel is built on a protruding mass of trap con- 

 glomerate, amorphous, and irregularly traversed by fissures. 



The paste of the conglomerate is chiefly compact felspar, variously coloured, and sometimes mot- 

 tled, but most commonly of a reddish hue, apparently much charged with iron ; but in some places 

 it consists of very fine-grained, compact greenstone. The base envelopes fragments of limestone, 

 mostly angular, sometimes as large as the head, and even larger, also fragments of trap corre- 

 sponding more or less in composition with the paste. Among these may be noticed also basalt with 

 shining facets of small and minute grain. In the trap, calcareous spar appears as the most common 

 ingredient, and portions of green earth are also incidentally diffused. Where the calcareous spar 

 has decayed, the rock is porous and vesicular. To the north of Castle Carrig O'Gunnel hill, is a 

 lower hill, which consists of calcareous conglomerate, a base of limestone with some green earth 

 diffused, inclosing numerous fragments of trap. In these conglomerates occur numerous crinoidal 

 remains ; also broken bivalves ; and I noticed one specimen of Cyathophyllum. 



The trap conglomerate of Knocknea resembles in many respects that of 

 Carrig O'Gunnel, but it is disposed in tabular masses, nearly horizontal, dip- 

 ping only a few degrees to the north-east. A defile separates this hill from 

 that of Cahirnarry, on the north. The latter consists of compact basaltic 

 greenstone, containing acicular crystals of glassy felspar, and grains of horn- 

 blende or augite, and it is disposed in a rudely thick, columnar form, without 

 distinct sides. To the north-east of Cahirnarry is a lower hill, which appears 



VOL. V. SECOND SERIES. G 



