KiNAHAN — Killary Bay and Slieve Partry Silurian Basin. 719 
altered them into granite and gneiss was in force at a later time 
than the general action that metamorphosed the County Eocks — or in 
other words, there were two periods of metamorphic action, one being 
general, while the later was restricted in its area. In the county Gal- 
way I saw no distinct facts to lead to such a conclusion, but in north- 
east Mayo, where the rocks are very similar, proofs were forthcoming ; 
while, if we go further north into the county Donegal, it can be 
ocularly proved that the granite, with its associated gneiss, is nearer 
than the associated schists.^ 
Both in Galway and Donegal, at the southern margins of the 
granite tracts, there is a bedded-like structure ; that is, the granite 
consists of bedded-like masses, each of which has a more or less distinct 
appearance and composition, while northward, in both areas, the 
change from the granite through the gneiss into schists is gradual. 
This is more marked in Donegal than in Galway, as in the first the 
area is divided into two, by the great Glenbeagh fault, northward and 
southward of which this triple system is found,^ 
That the Galway rocks, south of the Glifden and Oughterard road, 
are for the most part metamorphosed sedimentary rocks appears to me 
self-evident. The reasons for this assertion will first be given, and 
subsequently I will reiterate my former reason for supposing that they 
are younger than the rocks of the Bennabeola {Twelve Pins.) 
To the extreme north of the area now under discussion in the neigh- 
bourhood of the lakes (Ballynahinch, &c.), of the Glifden and Oughterard 
valley, there is a limestone and schist series in which are subordinate 
cpartzite. This series occurs in all the different sections, and can be 
traced for miles, although shoved northward and southward by nume- 
rous faults. It is scarcely possible to believe that this constant 
relation of one bed to another could be due to anything but original 
deposition, '^o attenuation due to shearing could give similar results ; 
no process of shearing, even if aided by molecular changes, could have 
1 In Donegal, as in Galway, the granites are of different ages. There is the 
granite, the adjunct of the granitic gneiss— two distinct granites newer than the 
gneiss, but pre-Ordovician ; and a post-Ordovician granite, much newer than the 
others ; as the veins and elvans from it, in the Dunfanaghy district, are newer than 
the upthrusting and other faults of that area. 
2 Similarly, in S.E. Wexford, we find in the Saltees, bedded-like granite, while 
to the northward, at Carnsore, the granite graduating into granite gneiss, and the 
latter into schists. These Wexford rocks, as I have previously pointed out, are 
probably pre- Cambrian ; that is, they represent one of the groups belonging to the 
Algonkians of the United States American Survey. 
