J'862.] . JTJKES — ^EITER-VALLETS.- 389 



ten miles above the point where it falls into the Lee. The united 

 waters then run due east down to the city of Cork, where they begin 

 to be affected by the tide, that would naturally flow further up, 

 bat is prevented by miU-dams. Just below Cork the river crosses 

 from the north to the south side of the limestone valley, through a 

 low limestone ridge in its centre, and then forms a wide expansion 

 of brackish water which goes by the name of Lough Mahon. 



The limestone valley of Cork is bounded on the north and south 

 by ridges of Old Eed Sandstone running from "W. to E., and termi- 

 nating in the latter direction on the coast on each side of Youghal 

 Bay. The distance from Crookstown to Youghal is more than 40 

 miles, and the strike of the rocks is due east and west throughout 

 that distance. The form of the Umestone vaUey, and of the Old 

 Eed Sandstone ridges, which follow the strike of the rocks, is exactly 

 similar the whole way, but aU gradually lowering towards the east. 

 Near Crookstown the highest points of the limestone are sometimes 

 over 200 feet, while the Old Eed ridges rise to 600 or 700 feet. 

 Near Cork the limestone reaches occasionally to 150 feet, while the 

 Old Eed attains to 400 and 500. Near Castle Martyr the limestone 

 has only one eminence of so much as 118 feet, and the heights of 

 the Old Eed Sandstone ridges do not exceed 300 and 400 feet. 



The height of the southern ridge is generally inferior to that of 

 the northern one ; and a few miles to the S.E. of Cork this southern 

 ridge is cut across by two ravines with precipitous sides, like those 

 described on the Blackwater, but not so high or extensive. These 

 two ravines are known as Passage West and Passage East ; and the 

 part of the Old Eed Sandstone ridge between them is called the 

 Great Island, — Cove or Queenstown standing on its southern slope. 

 To the south of that ridge we again find ourselves in a longitudinal 

 limestone valley running E. and W. across Cork Harbour, from Carri- 

 gaHne by Cloyne, into BaUycottin Bay. This, however, is more 

 broken and irregular than those to the northward, in consequence 

 partly of the coming-in of the Carboniferous Slate, and partly of the 

 more rapid folding of the rocks. It is, however, bounded on the S. 

 by another anticlinal ridge of Old Eed Sandstone, which strikes due 

 .east from the iaterior of the country, and terminates at the BaUy- 

 cottin Islands. (See Map, PL XIX.) 



This ridge is also cut across in the middle by a north and south 

 ravine with precipitous sides, forming the entrance to Cork Harbour ; 

 and it is through this that the sea gains access to that harbour, and 

 from that through the two Passages into Lough Mahon. 



As in previous cases, if we were to fill up the ravines of the two 

 Passages, the Lee must inevitably flow down the limestone valley 

 past Middleton and Castle Martyr into Youghal Bay. Similarly, 

 if the ravine that forms the mouth of Cork Harbour were to be 

 closed, whatever water ran into the basin must then proceed down 

 the valley to BaUycottin Bay ; and neither of the three ravines that 

 thus cut at right angles into the limestone vaUeys could have been 

 formed by any rivers running down these valleys while they had 

 anything at aU approaching to their present low level. 



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