116 THE LAKE-BASINS OF IARCONNAUGHT. 



avalanches, often extend into valleys. Some of these 

 must at one time have stretched across the valleys, 

 ponding up masses of water, and thereby forming lakes. 

 Now, however, in most cases, the stream-courses 

 having gradually become deeper and deeper, the bars 

 have been cut across, and the original drainage of the 

 valley is restored ; but not in all cases, as, for instance, 

 Lough Inagh, Connemara, which is separated from 

 Derryclare Lake by masses of moraine drift, to the 

 bottom of which the connecting river has not as yet 

 excavated its channel. 



The fourth class of bars are meteoric. Such bars 

 most writers appear to ignore, yet they often form 

 marked features, and their formation can in many 

 places be studied. A bar partly meteoric and partly 

 lacustrine may be formed when a torrent flows into 

 a lake and makes a delta, called in Ireland a srah 

 i.e., the level land at the inver or mouth of a river or 

 stream, usually covered during freshets. A srah 

 forms in a wide lake by the waters during floods 

 levelling the surface of the detritus as it is brought 

 down ; but in a narrow lake a bar may form across it, 

 and if the original embouchure of the lake is after- 

 wards lowered, two sheets of water form, one with a 

 higher level than the other, and in Ireland such a 

 lake is generally called Lough-a-voul or Lough-aw- 

 woul (anglice, the lake of the two spots). 



Other bars may be due to detritus carried down by 



