KiLROE — The Shannon : its Course and Geological Histovy. 85 



which may be briefly summarised as folio ays, in so far as they aid 

 us in the present inquiry: — 



1. The surface of the region aiffords proof of a prolonged Con- 

 tinental epoch — following "a movement characterized by folding and 

 overthrusting " with east and west axes,^ " essentially of an elevatory 

 type," which " was the direct cause of enormous denudation between 

 Carboniferous and Triassic times." So far as Mr. Strahan could 

 recognize, no valleys eroded by the drainage of this period can now be 

 pointed to. This was followed by — 



2. A period of submergence, with the piling up of Upper Creta- 

 ceous strata to such a thickness as would, if at present existing, cover 

 all Wales, except a small area about Snowdon. " All the features in 

 the Palaeozoic strata were blanketed over"; and the elevation into 

 land of the Secondary (and possibly early Tertiary) strata became the 

 occasion of the new river-systems which adjusted themselves with 

 complete disregard to the older valleys and ridges. 



3. The direction of these Tertiary river-systems was determined by 

 a north-east and south-west bulge in the region of Cardiganshire — 

 that is, an anticlinal axis in the direction of the ancient Caledonian 

 foldings, and of post-Oligocene and pre-Pliocene date. 



In the case of Ireland much could be said regarding the surface upon 

 which Upper Old Eed Sandstone and Carboniferous rocks were laid 

 down, that is regarding denudation in Devonian times ; and it is 

 remarkable how little we know concerning the results of denudation 

 during the " great Continental epoch" of post-Carboniferous, pre- 

 Triassic period. We know that the Carboniferous strata had been almost 

 entirely cleared away from part of the area in the north-east of Ireland, 

 where I^ew Eed Sandstone and I»[ew Eed Marl now exist ; and as the 

 part referred to falls within lines roughly drawn from the Head of 

 Strangford Lough and from Cushendall, to Kingscourt as apex of a 

 triangle, this area may, perhaps, be suggestive of a shallow pre-Triassic 

 bay — a hollow resulting from river-denudation. The clearing away of 

 Carboniferous rocks from parts still further west may be due to later 

 denudation. 



The existence of Triassic rocks clothing denuded Silurian and 

 Carboniferous strata alike, their uniformity in character, the apparent 

 sequence of strata upward through Lias to Cretaceous, and the 



^ The Ilercynian of Bertrand (Bulletin, Soc. Ge'ol. de France, series 3, tome 

 xvi., p. 570), the Armorican of Lapworth. 



