242 The Irish Naturalist. 



examination and consideration, he found that the transverse 

 valle5^s must have had a much more recent origin than the 

 longitudinal ones. 



A similar theory to that abandoned by Jukes was adopted 

 by Prof. Hull to account for the Scalp. He considered that 

 in the Co. Dublin there was high land to the northward, the 

 drainage from which excavated the Scalp. He said nothing 

 of the parallel valleys, such as those of the Slaney, etc., but, 

 presumably, they ought also to be included. His view as to 

 the Scalp seems now to be also adopted by Professors Sollas 

 and Cole. 



It seems to me indisputable, that the plain of Dublin was 

 at one time much higher than at present, as a vast thickness of 

 the Carboniferous limestone has been denuded away, and also 

 of the Coal-measures, the latter alone being more than 4,000 

 feet thick. But at what time did this great denudation take 

 place ? And during this period of denudation, at what time 

 was the granite ridge exposed? It is self-evident that the 

 Granite, and its adjuncts, the Ordovicians, and the other 

 older rocks, were protrudes prior to the accumulation of the 

 Carboniferous rocks ; but, at the same time, it appears highly 

 improbable, that at the time when there were high Coal- 

 measure hills in the Co. Dublin, an iota of the old rocks 

 came to the surface, the granitic and associated rocks never 

 having appeared until after the envelope was removed ; that is, 

 not till after the Coal-measure hills of the Co. Dublin had dis- 

 appeared. It cannot be denied that the granite ridge was a 

 margin of a basin in the Carboniferous sea, as we find the 

 littoral conglomerates of the Carboniferous high up on it ; but 

 was it always land during the Carboniferous epoch ? or was it 

 so near the surface as to be susceptible of denudation ? that is, 

 while the Carboniferous hills were high enough to send their 

 drainage southward.' 



It has been suggested, I think, by more than one authority, 

 that the Irish Coal-measures were denuded to form the lyias 



* It is not only possible, but to me it seems probable, that old rocks, 

 pre-Cambrian, Ordovician, and granite, formed hiUs margining the plain 

 of Dubhn to the south, and that of Kildare, Carlow, and Kilkenny to the 

 east. This is proved by the blocks of granite found in the Kinimage 

 limestones ; but that the Carboniferous rocks extended over these hills 

 seem to be problematical, as the Carboniferous rocks in Co. Wexford and 



