THE LAKE-BASINS OF IARCONNAUGHT. 121 



going on at the present day, but also, what appears 

 to be its work in ages long past can be recognised. 

 Marine denudation has left its records in the raised 

 gravel-bars and beaches, in the terraces on the hill- 

 sides, and in the cooms and corrys at similar eleva- 

 tions, not only in the hills of G-alway, but also in the 

 hills of Clare, Limerick, Kerry, Cork, and other moun- 

 tainous places in Ireland, while at the present day 

 similar work is being accomplished on the coast-lines. 

 Glaciers are now doing no work ; but that they once 

 existed is proved by the dressed hummocks and the 

 planed, grooved, etched, and polished rock surfaces. 

 It is quite palpable that the rocks of larconnaught 

 have suffered at successive periods from the disturb- 

 ances due to the movement in the earth's crust, as 

 they are not only folded and contorted, but also faulted 

 and displaced to a very remarkable extent. Some 

 of the faults must be very ancient, as the " fault- 

 rock " in them was metamorphosed along with the 

 associated rocks ; while others are post-glacial, as was 

 pointed out by our colleague Mr R. Gr. Symes, F.G.S., 

 as they displace the ice-formed drift. These last- 

 mentioned breaks are very instructive; 'for although 

 they form greater or less hollows, some over 100 feet 

 deep, and not more than from 10 to 30 feet wide, 

 yet in general, the horizontal displacement is trifling, 

 while in some it may be nil, as the same strata at 

 opposite sides of a ravine may face one another, while 



