of the North of Ireland. 163 



attains the elevation of 450 feet above the sea ; in the adjoin- 

 ing mountain called Donald's hill, its upper limit rises to 900 

 feet ; it occupies nearly the same level in Benbradagh, and at Crag- 

 nashoack the southern point of the chain gains its greatest height, 

 being there 1589 feet above the sea. In this mountain the sand- 

 stone and basalt are in contact, the chalk being deficient. Cragnash- 

 oack and Fairhead are, it is believed, the only instances In this dis- 

 trict where the trap is seen decidedly reposing on any other 

 rock than the chalk. 



The sandstone of Benyavenagh, of Kedy and of Donald hill, is red, 

 slightly variegated with yellowish stripes of a rather loose texture ; 

 it has a calcareous cement, and contains specks of mica. 



The sandstone of Benbradagh has the character of sandstone slate, 

 (he texture coarsely granular ; colour greenish white ; with a calcare- 

 ous cement, and containing spangles of mica. It extends to Dungiven, 

 and probably reposes on the mica slate, which occupies the left 

 bank of the Roe ; its thickness in this hill cannot be less than 

 five hundred feet. About a quarter of a mile from Dungiven, 

 at the opening of Benady glen a sandstone conglomerate occurs, 

 probably connected with this formation. 



The insulated primitive district of Coolcroscrahan, which is 

 situated behind Benbradagh on the north east, appears to be en- 

 circled with a ring of sandstone and marie. 



In Cragnashoack, two varieties of sandstone may be traced, the 

 upper beds consisting of a coarse grey sandstone with a calca- 

 reous cement, while the lower strata are more distinctly slaty and 

 micaceous, and have a yellowish colour and a siliceous cement. 



From Cragnashoack the sandstone extends to the south, abutting on 

 the north east slope of Slieve Gallion. Near this point it appears to 

 repose upon the shell limestone of Desert Martin, ranging from 



X 2 



