22 Scientific Proceedings, Royal Dublin Society. 



miles to tlie westward of Letterkeuny, near Grartan Lake. Hence 

 the rocks lie in tlie following order : — 



1. Micalites and hornblendites, limestones and inter- 



bedded (?) hornblende rocks (diorites), all dipping 

 south-east, at from 50° to 60°. These belong to the 

 limestone-diorite series, hereafter more especially 

 mentioned. 



2. Unconformahility. 



3. Grreenish boulder-bed, 



4. Flaggy quartzite, 



5. dreenish boulder-bed, 1 ^.^p-^^ g^ g_ ^^ ^^ l^c 



6. Flaggy quartzite, 



7. Greenish boulder-bed, 



8. Flaggy quartzite, 



9. TJi^thrust from the south-east. 



In the Boulder-beds (Nos. 3 and 5) the blocks and fragments 

 are in general not very frequent, while the exposures are capped 

 by slight thicknesses of flaggy quartzite (Nos. 4 and 6) , the inlying 

 blocks being principally granitic gneiss and foliated granite, 

 similar to those found in the country to the northward. But, in 

 addition, there were observed small pieces of gneissose quartzite, 

 hornblende rock, &c. In the Boulder-bed (No. 7) the majority 

 of the inliers observed were of a reddish, or pinkish, fine, nearly 

 micaless granite, similar to the vein-rocks in the granite country to 

 the north-westward, and also to the already-mentioned irregular, 

 thin granite veins in the rocks of the Gregory Hill series. As- 

 sociated with these are pieces — some of considerable size — of 

 gneissose quartzite and granitic gneiss, similar to those in the 

 country to the north-westward and northward. In this locality, 

 as also elsewhere, the greenish matrix seems to have been made up 

 of the debris of the underlying schists belonging to the Older 



occur ; while south-east of Glen Lough, to the west of Mulroy, there is a limestone 

 that in one place seems to belong to the Great quartzite ; while miles to the south- 

 west, in the barony of Banagh, Mr. Kilroe has found Boulder-beds which in places 

 are similar to those described above ; but others are limestones containing boulders. 



These Boulder-beds of Fanad are very similar in contents and appearance to some of 

 the shingly beaches at present existing on the western coast of the northern portion of 

 Inishowen (Lough S willy). 



