332 Scientific Proceedings, Royal Dublin Society. 



It has been already stated that it seems very possible that the 

 two principal reefs crossing Bray Head are disconnected portions 

 of the same. This is only a surmise on which very little direct 

 evidence can be produced. Between the two reefs there is a 

 great similarity, and the sequence of rocks in connexion with 

 both presents a general similarity. However, below the Brandy 

 Hole reef there is the greenstone dyke that is not to be found 

 below the northern reef. This may be due to the dyke being a 

 later intrusion, probably after the disconnexion had occurred, 

 and this is supported by the fact that the dyke is not to be 

 found under the western portion of the Brandy Hole reef 



At first sight there may appear to be a difficulty in detecting 

 any line along which such a fault could cross the hill. But 

 on closer examination, it appears very possible that the outcrop 

 of this fault, which fault would dip south at a low angle, runs 

 nearly parallel to that of the strata and along the hollow south 

 of the more northerly reef, and instead of extending to the shore 

 line at Bray Head, it turns south down the slope of the hill 

 towards the Brandy Hole ; this sudden flexure being caused by 

 .the breaking up of the strata along the numerous joints and 

 breaks that cross their strike, and the subsequent removal of 

 that portion lying above the plane of the main fault and east of 

 some of the more marked of these breaks. The bearing of this 

 main fault would be about E. and W., while it would be along it 

 that the cave known as the Brandy Hole extended. On the 

 westward slope of the hill, the sections and evidence in connexion 

 with this fault are very obscure, as the glacial drift extends for 

 some distance up the slopes of the hill, and above this there is 

 in many places a thick covering of meteoric drift. 



