[ i6] 

 DENUDATION AT CUI.TRA, CO. DOWN. 



BY MARY K. ANDREWS. 

 (Read before the Belfast Naturalists' Field Club, December 20th, 1892) 



Tradition, history, and geological evidence all bear testimony 

 to the continued interchange, within certain limits, of land 

 and water. Although the deep depressions of the ocean and 

 the main trends of the land seem, from the very earliest geo- 

 logical periods, to have preserved their same general positions 

 on the globe,' yet a careful comparison of the upheaved strati- 

 fied formations, with the layers of gravel, shells, sand, and 

 mud deposited in the comparatively shallow seas around our 

 coasts, leaves little doubt that very large portions of our land 

 areas, were, at one period or another, laid down upon the floor 

 of the sea. Subject to the action of internal forces they have 

 experienced many oscillations of level, insular conditions at 

 one period predominating, continental at another; crustal 

 movements, modified by denudation and deposition, govern- 

 ing the relative levels of land and sea. 



It was a fundamental proposition of the Huttonian Theory, 

 " That in all the strata we discover proofs of the materials 

 having existed as elements of bodies, which must have been 

 destroyed before the formation of those of which these materials 

 now actually make a part." ^ One portion of the earth's sur- 

 face is slowly and constantly wasted, denuded, and transported 

 to the sea, whilst another portion, formed from similar ma- 

 terials of pre-existing land, is as constantly consolidated and 

 raised to take its place. In this sequence of events, protracted 

 through an indefinite period of time, Hutton recognized one 

 general constant order in nature, the ruins of an older world 

 always forming the foundations of a newer. In the decay of 



^ " Geographers must, for the present, be content to take the world as 

 they find it. What we do know is that our lands are distributed over the 

 surface of a great continental plateau of irregular form, the bounding slopes 

 of which plunge down more or less steeply into a vast oceanic depression. 

 So far as geological research has gone, there is reason to believe that 

 these elevated and depressed areas are of primeval antiquity — that they 

 antedate the very oldest of the sedimentary formations." — Address to the 

 Geographical Section of the British Association^ 1892, by Professor James Geikie, 

 Lly.D., etc. 



-Playfair's "Illustrations of the Huttonian Theory," p. 23. 



