554 A. H. Oreen — Geology of Co. Donegal. 



Then I saw that I had found out nothing new — which was at first 

 disappointing — but, also, that I had good names on my side, which 

 was comforting ; but it seemed to me that there might still be some 

 use in publishing my paper, because the papers mentioned are 

 mainly mineralogical, and the fact that the granite is bedded, though 

 most strongly insisted on, comes out in them somewhat incidentally ; 

 because I flattered myself that it was just worth while putting on 

 record that I had independently come to the same conclusion as 

 previous observers ; and, lastly, because I wished, even at the risk 

 of tiresome iteration, to recall the attention of geologists to a district 

 so eminently suited to throw light on the vexed question of the 

 metamorphic origin of certain granites. 



My head- quarters were at Dunlewey, in the north-west corner 

 of the county. The general structure of the country and lie of the 

 rocks is shown in the section. Fig. 1. While I believe the section to 

 be correct as far as the order in which the rocks occur, I should not 

 wish to commit myself positively to the statement that the quartz- 

 rock of Errigal is the lowest, and the granite the highest, of the 

 rocks shown on it. The dip is everywhere so steep, the folds so 

 sharp and sudden, and the possibility of inversion so great, that the 

 reverse may be the case. It was mainly on physical grounds that I 

 considered the order of superposition to be that adopted : the abrupt 

 westerly face of Errigal has so much the look of an escarpment, and 

 its less steep easterly side so much of the character of a dip-slope, 

 that, after considerable hesitation as to which was the highest and 

 which the lowest rock in the district, I at last thought it most 

 probable, mainly on the above ground, that the dip was on the whole 

 towards the east, and the rocks, therefore, in that quarter the highest 

 in the series. 



"Whether this or the reverse be the case, however, matters little to 

 the main object I have in view; the arguments I shall bring forward 

 in favour of the bedded character of the granite will hold equally 

 good, whether that rock be the highest or lowest in the district ; at 

 the same time, if this granite can be shown to overlie conformably 

 undoubtedly stratified rocks, it will be an additional fact in favour 

 of its metamorphic origin. The strike of the district is remarkably 

 constant, never departing more than a few degrees from magnetic 

 east and west, the variation being about 24° or 25°. To the east of 

 the quartz rock of Errigal ^ we have a belt of country mainly made 

 up of mica-schist, with beds of grey crystalline limestone here and 

 there, and a few occasional patches of white marble, seemingly of 

 very limited extent ; beds of quartzite also occur. Beyond this belt 

 lies a large tract of rock, the mineral composition and physical 

 features of which are those of granite, and as such it has been 

 described and coloured in Geological Maps. I shall without prejudice 

 speak of it as granite. 



Along the eastern margin of the belt of mica-schist, we find dis- 

 tinctly interstratified beds of a rock, which in hand-specimens it 



1 So spelt on the Ordnance Map. I believe that Aracal represents more nearly 

 this Celtic name, the meaning of which is "Beware." 



