TOPOGRAPHY AND GEOLOGY. 7 



The crumpling of Cork and Kerry was of immense significance to the 

 scenery of southern Ireland. The crests of the anticlinals were at first 

 formed of Coal Measures, of Carboniferous Limestone, and, in places, of 

 Carboniferous Slate. These rocks were stripped off by weathering, and the 

 Old Red Sandstone lay revealed below (Fig. 4). 



The action of the atmosphere was hereupon greatly retarded, while it 

 could still carve away at the softer and often soluble strata that occupied the 

 synclinal folds. Hence the anticlinals weathered out as ridges, running east 

 and west, and the synclinals were worked down into valleys. The structure 

 of the W'hole south is as simple as that of the Jura Range, when we take a 

 broad survey of that classic area. 



The beds are, however, so compressed together as to be often overfolded ; 

 and numerous minor wrinkles accompany the main and obvious ones. In 



Courses of Rivers J^^^^ f,^^^^^^ ^'^^' ^I'^J'^^'^""'^ structure is evidenced 

 . « ,, by the courses of the Bandon River, the Lee, the 



m boutnern g^^^^^ ^^^ Upper Blackwater, and the lower portion 



Ireland. ^^ ^-^^^ Suir. All these rivers run east along synclinal 



hollows, which are mostly still filled by Carboniferous Limestone. West of 

 the watershed that passes through the Boggeragh and Derrynasaggart 

 Mountains, the streams run similarly along synclinals to the Atlantic ; but 

 their former valleys have been largely invaded by the sea, owing to subsi- 

 dence of the coast in comparatively recent times. 



The courses of the rivers in southern Ireland at the present day are thus 

 clearly dependent on the direction of the Hercynian folds. But some of 

 them, like the Lee and the Blackwater, seem at last to defy the anticlinal 

 and synclinal axes, by turning abruptly south and cutting across them. Pro- 

 fessor Jukes long ago supplied the explanation of this bending of the 

 streams at right angles to what appears to be their proper course. The 

 earliest drainage from the mass that was upheaved at the close of the Car- 

 boniferous times gave us a system of streams running north and south. The 

 general wearing down of the surface by denudation, in long subsequent 

 times, carved out the systems of east-and-west valleys in the synclinals, and 

 in these the tributaries of the main streams ran. But certain southward- 

 running streams, having got the start, and working down the steep slope of 

 the countr}^ kept ahead of the tributaries, and maintained their own valleys 

 at a lower level. Hence, although these tributaries spread farther and 

 farther back, and became in time the most important portions of the rivers, 

 their waters were still turned south where they joined the original gorges. 

 As Professor Davis shows us, moreover, only the more active of the south- 

 ^\•ard running streams would cut their way down at a sufficient rate. While 

 the valleys grew deeper along the synclinals, some of the tributaries would 

 altogether fail to get into their original main streams ; the latter would be, 

 as it were, " beheaded," and would dwindle, while their former tributaries 

 would swell the volume of the nearest successful primary stream. 



Hence the rivers of southern Ireland, and, indeed, of Ireland generally, 

 are older than the present form of the surface. General denudation has 

 lowered and widened their valleys in some places, leaving other parts of the 

 adjacent country standing at a higher level ; and the rivers seem to cut 

 across mountain-ridges, because the hard rocks of these ridges have resisted 

 denudation, while the gathering-ground of the rivers, up stream, has been 

 more rapidly worn down. 



The original Hercynian mass was far more continuous than the present 

 ridges, which have been carved out by ages and ages of denudation. We 



