Lower Palaeozoic Bocks of the South-East of Ireland. 571 



seated rocks of all other localities. It is, however, remarkable that in oiir dis- 

 trict this amount of denudation had not only been begun, but almost completed, 

 at a very early geological period, namely, before the commencement of the Car- 

 boniferous period. 



The bare granite formed the floor of the sea in which the beds of Old Red 

 Sandstone and Carboniferous Limestone were deposited, and the surface of the 

 ground of the islands which rose from that sea ; just as bare granite would now 

 form the bottom of the sea and the surface of the islands, if the Carboniferous 

 rocks were stripped off, and the country depressed again a few hundred feet 

 beneath its present level. 



The present surface of the ground in our district is in many parts a very old 

 surface; it existed very nearly in its present form before the deposition of the 

 Old Red Sandstone. It was, however, once much more covered by an extension 

 of the beds of the Old Red Sandstone and Carboniferous Limestone than at 

 present ; as is proved by the existence of some outliers of those rocks beyond 

 their general boundary. The most remarkable of these outliers is a patch of 

 Carboniferous Limestone resting on Cambrian rock, at Taghmon, in the county 

 of Wexford, six or seven miles from the nearest boundary of that formation.* 



It is indeed probable that the present outline and contour of the ground of 

 the ivhole of our district was very nearly what it is now, before the period of the 

 Old Red Sandstone, any subsequent erosion and denudation having been very 

 slight compared with that which had taken place previously to that period. 



It follows from this, that, however intrusive some of the igneous rocks of the 

 Lower Palasozoic district may be, and however much younger than the aqueous 

 rocks with which they are in contact, yet, as there is nothing to warrant us in 

 supposing them to have had an origin subsequent to the process of denudation, 

 the whole of them are older than the Old Red Sandstone. 



The Lower Palteozoic district must doubtless have partaken to some extent 

 of the subsequent movements of disturbance which have affected the upper Pa- 

 leozoic rocks of the immediate vicinity, and may have been more or less shaken 

 and dislocated by all the disturbing influences that have vibrated through this 

 portion of the globe since the Cambro-Silurian period. It must also have suf- 

 fered to some extent by the denuding action which has swept away so large a 

 portion of the Upper Paleozoic rocks from the immediate neighbourhood. One 



* See " Journal of the Geolosical Society of Dublin," vol. vi. p. 178. 



