264 The Irish Naturalist, September, 



from west to east over the greater portion of their course and 

 then turn abruptly from north to south when the primitive 

 north-and-south channels cutting across the sandstone are 

 reached. The most remarkable example of this curious river 

 system is the course of the Blackwater, which rises in the 

 Kerry mountains; and after a west to east flow of 70 miles in 

 the limestone valley running north of the Mangerton axis, 

 turns at Cappoquin suddenly at right angles to its former 

 course and reaches the sea at Youghal through a primitive 

 channel across the sandstone ridge of Drum. The same 

 principle (first worked out by Jukes in 1862) governs the 

 courses of most of the rivers of the South of Ireland. In late 

 Tertiary times, after erosion had wrought deeply, the land 

 sank, submerging the mouths of many of the river valleys 

 and producing those striking sea-inlets of which Passage East 

 and Passage West and the strait connecting Cork Harbour 

 with the Atlantic afford excellent examples. 



The Glacial deposits of the district surrounding the city of 

 Cork have recently been mapped by the Geological Survey, 

 and during the progress of this work a most interesting dis- 

 covery was made of a pre-Glacial raised beach. This beach 

 (which has been worked out by Messrs. Wright & Muff, of 

 the Geological Survey), has been traced from Baltimore to 

 Carnsore Point, and presents the following features : — A rock 

 shelf usually about twelve feet above sea level, and in places 

 extending seawards up to fifty feet from the base of the cliff. On 

 this rock shelf and in the angle formed by the pre-Glacial 

 cliffs occur pebbles and sand often to a depth of several feet. 

 Over these marine deposits comes a thick layer of "head," 

 proving that an elevation of the land had taken place, as the 

 "head" is recognized as rock-rubble formed by sub-aerial 

 waste during severe climatic conditions. The "head" is 

 covered by Boulder-clay of Cork type, and is in its turn covered 

 by an upper "head." This beach, as the most important 

 geological discovery in Ireland for a number of years, was 

 studied with great keenness by those members of the Con- 

 ference interested in geology. Every opportunity was taken 

 to visit the most representative sections, and Clonakilty, 

 Simon's Cove, Ballinglanna, The Old Head of Kinsale, Church 

 Bay, Passage East, Youghal Bay and Whiting Bay were 



