140 Tur Rev, MAXwewt H. Coser, 
within, what may be called, comparatively narrow limits. The 
facts that the granite has been intruded into the Lower Silurian 
rocks, and that the slates of that formation have been meta- 
morphosed all along the border of the granite into mica schist, 
evidently by the action of the granite, show that the intrusion of 
the granite was later than the formation of those rocks. On the 
other hand, the facts that, in the Co. Kilkenny, the Old Red 
Sandstone reposes undisturbedly on the granite and has not been 
altered thereby, and that its beds sometimes contain a quantity 
of granitic pebbles and detritus, show that the protrusion of the 
granite took place before the deposition of those rocks. 
The main granite exposure includes the principal mass, with 
the highest summits, of the 8. Dublin, Wicklow, and Wexford 
hills; while the Silurian rocks form lower ground on each side, 
with some subordinate hills. This, in connexion with the fact 
that the general strike of the Lower Silurian rocks is very nearly 
parallel with the length of the granite exposure, on each side, 
might, at first sight, give rise to the idea that the granite, while 
being forced into the Silurian strata, had broken through them, 
upheaving them and throwing them off on either side, so as to 
make them dip away in both directions. But what evidence 
there is on the point bears against this supposition. The granite 
has nowhere brought up the underlying Cambrian rocks on its 
flanks; nor has it thus brought up the lower of the Silurian 
rocks. It is true that the metamorphosed Silurian slates, close 
along the sides of the granite, usually dip away therefrom, on 
each side; but notwithstanding this, the Silurian strata on the 
western side of the granite, though evidently much folded and 
contorted, seem nevertheless to dip, as a whole, towards the 
granite ; so that the higher beds come against it; and it would 
appear that in the Co. Wexford, also, on the eastern side, they 
are the upper beds which border the granite (although it is not 
so, northward of that, in the Co. Wicklow.) Again there are 
patches of altered Silurian slates lying on some of the highest 
parts of the granite hills, including the very summit of Lugna- 
culliagh itself, 3,039 feet, the highest point of all. It is just at 
the highest part of the granite, where it has escaped denudation, 
that we find the schist still lying upon it; while on the other 
hand, itis just where the valley of the Slaney cuts across the 
range of the granite hills, and the denudation has been greatest, 
