THE LAKE-BASINS OF IAKCONNAUGHT. 123 



breaks, faults, or other shrinkage fissures, as well as 

 all the transverse guts and bays. This is exemplified 

 in the accompanying map of Lough Conga (Map, 

 fig. 15, PI. II), the lake being specially selected on 

 account of its outline being so irregular. All the 

 lake-basins in this country widen or contract in 

 accordance with the number of faults or joint-lines 

 which meet or cross in the area occupied by them. 

 If such lines were numerous, close together, and 

 crossing one another, a considerable portion of the 

 rocks would be broken up, and more or less easily 

 removed, either by ice or sea action ; while if only 

 one line or two parallel lines existed along which the 

 force could act, the hollow excavated would be long 

 and narrow. All these cases are exemplified by 

 the larconnaught rock lake-basins, some of which 

 are wide, others long and narrow, many most ir- 

 regular in outline, while all coincide with the 

 associated features of the country due to the breaks 

 and faults in the rocks. 



After rocks have been broken up by faults and the 

 like, marine action in a shallow basin could sweep 

 or suck out the broken materials ; but in places of 

 considerable depth it appears incapable of executing 

 the necessary work. Meteoric abrasion would take 

 an incredible length of time to do it, as it would first 

 have to disintegrate the blocks and fragments, while 

 the detritus would have to be removed by wind, or 



