146 THE Rev. MAXWELL H, CLosE, 
came up. irregularly into the Lower Silurian strata, we 
cannot form any idea what thickness of the latter may 
have covered those places when the denudation began; though it 
was probably something considerable. But there is good reason 
for believing that, near the town of Wexford, the whole thickness 
of the Lower Silurian formation of this region was stripped off 
the Cambrian rocks before the deposition of the Old Red Sand- 
stone in that vicinity. The Silurian strata seem to have been 
there laid down evenly on the surface of the already contorted and 
denuded Cambrian mass; and it is just in that neighbourhood, 
alongside of the Cambrian boundary, that we have the clearest 
evidence of the great thickness of the Silurian rocks, viz., per- 
haps ten or twelve thousand feet. ‘Some such thickness of Lower 
Silurian beds must have stretched over the now exposed Cam- 
brians, near at hand, and by far the greater part must have been 
removed by the denudation of which we are now speaking, as is 
shown by the remains of the Old Red Sandstone which lie on 
the Cambrian rocks at a distance of only 1} mile from the 
nearest and lowest Silurian stratum. The re-exposing of the 
Cambrian rocks nearer Dublin must have been, likewise, chiefly 
performed by this denudation, though doubtless partly by that 
to be considered farther on. 
The fact that the Old Red Sandstone conglomerates near the 
granite in Co. Kilkenny and in Co. Waterford contain pebbles of 
that rock is another proof of the great denudation that had taken 
place before the deposition of these conglomerates ; since, as far 
as we know, true crystalline granite is formed only under the 
conditions of very slow cooling and great pressure, that is to say 
at a considerable depth beneath the surface. 
OLD RED SANDSTONE (?)—This may be but the basal or shore 
beds of the Carboniferous formation. Although there are four, 
and possibly five, presentations of these rocks in this district, they 
are all very small. This is on account of the (conformable) over- 
lapping which hereabouts runs through the whole series of Car- 
boniferous strata. The post-Carboniferous larger-scale distur- 
bances were, in this region, comparatively small (though not so in 
the 8. of Iveland) ; and it was only here and there that the later 
denudation was able to bring these underlying beds to the surface. 
No fossils have been found in them, 
