KiLROE — Silurian and Mefamorphic Rocks. 139 



it traverses alternating mica-schist and coarse gneiss-bands or 

 lenticular masses, passes close to the point where I found the 

 rounded pebbles in the fine-grained gneissose rock, and shows also 

 the stratigraphically overlying qnartzite. The northern part of the 

 section indicates the circumstances just explained. 



I concur in giving to the rock the name of quartzite, under 

 which it was represented when the ground was originally surveyed 

 in 1876, by Mr. McHenry, although it contains a considerable 

 proportion of mica, and some felspar; and in going eastward the 

 proportion of felspar grains increases, while that of the mica 

 diminishes, in beds which, though stratigraphically higher, are 

 obviously of the same qnartzite group. These beds are well to be 

 seen along the low, jagged cliffs near Cone Island. Crossing Broad 

 Haven, the entire section along the cliffs from Benwee Head, east- 

 ward to the Carboniferous boundary near Belderg, shows similar 

 variations from the purest type of qnartzite ; only at a point about 

 half way between the two points named, does purely silicious qnartzite 

 occur, but as part of the series. 



Passing across the vast peat-covered tract where the rock is rarely 

 to be seen even in stream courses, we reach the indistinct escarp- 

 ment of Glencalry, formed of the same gneissose-looking rock seen 

 near Erris Head, and here and there throughout the tract just 

 mentioned east of Broad Haven. This rock is here, also, correctly 

 described on the published map as micaceous qnartzite ; and it is seen 

 to pass under a series of beds consisting chiefly of mica-schist and 

 limestone, with some qnartzite bands, or single band overfolded and 

 repeated. The mica-schist — which here becomes obscured by the 

 supervention of Carboniferous strata — spreads out westward so as to 

 cover a wide area, and appears to form an important member of the 

 metamorphic series, forming Barnacuillew (875), Knocknalower (612), 

 and Aghoos (348) hills. A limestone zone marks the boundary of the 

 mica-schist near Aghoos, as well as at Glencalry ; it is to be seen at 

 Kilcommon Eectory, in the small stream draining Carnhill. This 

 boundary-line between the mica-schist and qnartzite passes around 

 the north shoulder of this hill, to the shore of Broad Haven, which it 

 crosses, is taken up again at Portnacally, and traced south-westward, 

 to become lost in the obscure ground north of Belmullet. North-west 

 of Belmullet, however, the circumstances observable near Erris Head 

 are repeated ; for on the coast near Scotchport Hock the coarse, 

 pegmatitic gneiss is again to be seen invading the passage beds from 

 the mica-schist group — portions of which are included in the coarse 



