KiLROE — The Shannon: its Course and Geological History. 77 



A sectional view of the riyer is given (figs. 1 and 2, Plate lY.), and 

 two lines representing the eastjand west watersheds — looked at as from 

 the east side. The profiles exhibit the striking variation in levels, of 

 points over which the watershed passes — the heights to which the 

 sandstone hills tower as compared with the slight elevation above the 

 sea and extreme flatness of the limestone plain. The section also 

 exhibits how insignificant is the fall between Lough Allen and the 

 estuary — some 159 feet, most of which is expended at the shallows of 

 Carrick-on-Shannon, Rooskey, Athlone, Meelick, and between Killaloe 

 and Limerick. The extreme flatness of the river between Athlone 

 and Meelick is such that, consequent upon the completion of the Suck 

 Drainage-works in 1892, it was found that the callows along the 

 Shannon above the confluence of the Suck at Shannonbridge were 

 much more liable to sudden and frequent floodings than they previously 

 had been. The more rapid discharge of the Suck waters into the 

 Shannon, before ordinary extra water had time to pass away, had the 

 effect of modifying the regimen of the main stream to an extent 

 which resulted in an action at law.^ 



The waters of Lough Eee stood some 10 feet higher within recent 

 times than they now do, as proved by evidence of solution, with under- 

 cutting of limestone blocks, to be seen about five miles north-west of 

 Athlone, close to the railway, in the townland of Cornaseer. Under 

 these conditions the lake must have been, perhaps, twice its width, 

 and for a considerable period. Its ancient surface-level is clearly 

 indicated by the caps of the mushroom-shaped blocks. 



The average rainfall in the Shannon basin, calculated for a period 

 of thirty years (1870 to 1899) is as follows:— 



At Eroadford in Clare, . . . 33-50 inches. 



„ Eirr Castle, .... 33-06 „ 



„ Mullingar, 36-502 „ 



„ Ahascragh, .... 40-40^ ,, 



Average for four stations, . . . 35-86 „ 



The stations in question are all at a low level ; if we had records 

 from some in the hilly regions of Lough Allen and around Lough 



^ La Touche versus The Suck Drainage Board. 



2 Rainfall at these stations was in part computed, observations there not 

 extending over the full term of thirty years. 



