CHAPTER XII. 



THE KIVER VALLEYS OF SOUTH-WEST IRELAND : THE 

 VALLEY OF THE WEALD, AND THE FIORD OF 

 KILLARY HARBOUR. 



IN a paper " On the Mode of Formation of some of 

 the River Valleys in the South of Ireland," * the 

 late J. Beete Jukes, F.R.S., suggested that subaerial 

 denudation was the principal carver of the physical 

 features of the south of Ireland. The reasons on which 

 this eminent geologist founded this theory may be 

 epitomised as follows : 1st, Limestone once existed 

 over the whole of the S.W. of Ireland. 2d, The 

 valleys are not connected with faults or fissures. 3d, 

 Marine denudation only acts with a broad, horizontal 

 movement, tending to plane down the land to its 

 own level. 4th, Marine denudation cannot produce 

 ravines or narrow, winding valleys. 5th, All glens, 

 ravines, and winding valleys have been excavated by 

 either ice or rain and rivers ; and 6th, That the in- 

 ternal forces of disturbance must have ceased to act 

 long before the present surface was formed. 



1 Quarterly Jour, of Geol Society of London, Nov. 1862, p. 379. 



