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 1J 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 S. of Ireland) ; and it was only here and there that the later 

 denudation was able to bring these underlying beds to the surface. 

 Ho fossils have been found in them. 



