54 PALEOZOIC TIME. [CHAP. V 



these truncated strata, we see that they probably once- 

 stretched far away into the interior of the Highlands." 



On the south side of the central Lowland tract the belt 

 of Lower Old Red is partly overlapped by the Upper divi- 

 sion, but from Girvan to the Pentland Hills it is faulted 

 against the older rocks, and there can be no doubt that 

 its original limit lay far to the south of its present 

 boundary. 



In the north of Ireland there are two areas which exhibit 

 a set of rocks which are similar to the Lower Old Red of 

 Scotland, one of these is a tract about thirty miles long 

 by ten wide, lying between Lough Erne and Pomeroy in 

 Tyrone ; the other is a very small tract on the north coast 

 of Donegal. 



In the south of Ireland there is some uncertainty about 

 the stratigraphical relations of the rocks which lie between 

 the Silurian and the Carboniferous systems. Such rocks 

 are only found in Kerry and Cork, and are known as the 

 Glengariff Grits ; they consist of hard green and purple 

 sandstones, with purple slates and some beds of conglome- 

 rate. In the Dingle promontory these beds conformably 

 succeed the Silurian, and are covered unconformably by 

 the conglomerates of the (so-called) Upper Old Red Sand- 

 stone. Further south, however, near Killarney, the upper 

 conglomerates are absent ; the highest Glengariff slates are 

 succeeded by the sandstones of the Lower Carboniferous 

 series. At Glengariff the Carboniferous slate has grey 

 grits and slates at its base (Coomhola grits), which seem 

 to rest conformably on the Glengariff slate and grit series. 

 Still further south, near Toe Head, the yellow sandstones 

 again come in between the Glengariff and the Carboniferous- 

 slates. 



Professor Hull believes that the Carboniferous conglo- 

 merates are overlapped southward by higher beds, and that, 

 these come to rest upon the Glengariff grits at Killarney 



