KiNAHAN — A New Beading of the Donegal Rocks. 23 



Period Rocks, the matrix in places being more or less quartzose, 

 like as we find more or less quartzose varieties in those schists. 



As the Boulder-beds in the Knockanteenbeg outlier are inter- 

 stratified with the quartzites, it seems to suggest that they are littoral 

 deposits that accumulated in the vicinity of land. {See section, 

 fig. 1, Plate III.) 



A curious suggestion in connexion with these Boulder-beds has 

 been made to the effect that they are of sole glacial origin, the 

 blocks being brought considerable distances by ice from Archaean 

 areas ; it being even stated that the red or pinkish f eldspathic rock 

 is the same as the feldspathic rock so characteristic of the pre- 

 Cambrian rocks of Erris, north-west Mayo. The feldspathic rocks 

 of Erris, however, are of the peculiar and rare shade of pink 

 rarely found but in limestones, and are only recorded as found here 

 and in a foliated granite near Lackagh Bridge, Co, Donegal. 



All these Boulder-beds of the Co. Donegal are totally devoid 

 of all the peculiarities of glacial accumulations ; whether on the 

 land or in water, while they are eminently characteristic of littoral 

 deposits; the contained boulders and fragments being nearly 

 always well water-worn and rounded, while the matrix in which 

 they are embedded is sand and silt ; the washings or detritus of the 

 associated older rocks. 



It appears ridiculous to go hundreds of miles to look for the 

 source of the boulders while rocks similar to them are found close 

 at hand.^ 



Still further south-west, in the neighbourhood of Lough Finn, 

 the basal-bed of the Grreat quartzite is also a greenish rock, but 

 the pebbles in it are few and small, none of the exposures having 

 any of the characters of a conglomerate ; in fact, more pebbles 

 were observed in some of the overlying quartzite than in it. 

 However, still further south-west, near Grlenties, the basal-beds 

 are more or less similar to the Boulder-beds already described ; 

 while to the south-west, in the barony of Barnagh, there are the 

 Boulder-beds — some having a limestone matrix — recorded by 

 Mr. Kilroe. These, however, have not been examined by me. 



1 Dr. Hyland has since examined the boulders in the Croghan district, and from 

 him I learn that the granite boulders have none of the characters of an Archaean 

 granite ; while they are identical with the granite he found in situ in the country to the 

 northward. 



