258 Scientific Proceedings, Royal Dublin Society. 



place at the close of the Ordovician period, and before the com- 

 mencement of the Carboniferous system. 



6. Thus the intrusion of the granite both of Wicklow and 

 Newry took place after the deposition of the Ordovician ; it had 

 already cooled and consolidated, at least for some distance inwards 

 from its outer surface, before the period of crush ; and it was foliated 

 together with the Ordovician, so long previous to the com- 

 mencement of the Carboniferous system, that by the time the Car- 

 boniferous limestone was in process of deposition, the overlying 

 Ordovician strata had been removed from it by denudation. 



The " soda-granites " of Wicklow and the granite of the Mourne 

 mountains have a different history. 



1. Neither are foliated at their margins. The " soda- granite," 

 which occurs near Aughrim, penetrates schists which have been 

 subjected to extreme pressure, as is shown by the perfect schistosity 

 developed in the associated igneous dykes. Notwithstanding this, 

 the granite, which is clearly exposed in a railway cutting near 

 Aughrim, shows no trace of " crush." 



2. The andalusite developed by contact metamorphosis in the 

 schists adjoining the Aughrim granite is not crushed : the planes of 

 foliation of the schists traverse it undisturbed. 



3. These granites are therefore later than the earth movements 

 which succeeded the deposition of the Ordovician rocks : that of 

 Mourne is in all probability of Tertiary age, as may be the soda- 

 granites of Wicklow, though, as I hope subsequently to show, this 

 is not likely 



