Physical Features. 59 



the edge of the escarpment to the sea are short and rapid in 

 their courses, carving deep valleys or notches in the edge 

 of the escarpment. County Down for the most part consists 

 of undulating hills of no great elevation, except in the 

 extreme south, where the Mourne mountains rise to a height 

 of 2,796 feet above the sea. In Down, the slope of the 

 river-courses is more even, and as they flow into the sea 

 they produce flats and become sinuous. These contrasts 

 between the two counties are due to the difference in the 

 nature and statigraphical characters and arrangement of the 

 rocks of the respective counties. Both counties have been 

 subjected to the same sculpturing and denuding agencies 

 in recent times, notably to glacial action, and subsequently 

 to the usual modifying action of aerial and aqueous 

 denudation. 



County Antrim generally may be considered as a land 

 owing its rocks to the Mesozoic and Cainozoic eras. 

 No great series of earth foldings or mountain building 

 strains have occurred in the county since the deposition 

 of its rocks. Numerous faults occur which may be traced 

 to the Eocene period, but the efforts towards rock crump- 

 lings or mountain building proved abortive ; the rocks 

 of our district could not resist the strain ; and the crust of 

 Mesozoic rocks, represented by the Chalk, broke into a 

 number of " floes," the black lava finding its way to the 

 surface through the wider fissures, converting them into 

 dykes. So rapidly and evenly did the Chalk yield under 

 this strain that the original horizontality of its beds of 

 deposition has been but slightly affected. The general 

 surface of the county may be described as "saucer-shaped"; 

 that is, the central area consists of a plain somewhat 

 depressed below the level of the edge or escarpment that 

 overhangs the coast line. This "saucer-shaped" character 

 is mainly due to the Pliocene or Post-Pliocene movements, 

 which broke up the old Derry-Antrim plateau and dropped 

 the basalt to the level of Lough Neagh. The edge of the 

 saucer or the escarpment presents a fine and almost 

 continuous geological section, basalt occupying the higher 

 portions, under which occurs the Chalk — sometimes little 

 more than a thin white line, but often of considerable depth, 



