KiLROE — The Shannon: its Course and Geological Histonj. 93 



Without attempting so bold an assumption — for we lack anything- 

 that could be admitted as sound evidence — we need not have much 

 hesitation in claiming that a glacier marking the latest stage of ice- 

 action in our region did pass through the gap. It may have been of 

 insignificant dimensions, as compared with Alpine giant glaciers, yet 

 that which formed Lake Iseo seems to have been insignificant as 

 compared to its predecessors. 



Just as the glaciers deposited moraines at difi'erent stages of 

 melting and recession in front of the Oglio Valley, so we find moraine 

 mounds at four points in front of the Killaloe gorge : — some of an 

 Esker type, south-east of Castleconnell ; others at O'Brien's Bridge, 

 representing, perhaps, a second stage of melting; a third at Birdhill, 

 representing a thii'd stage, and a mound at Killaloe, consisting chiefly 

 of sand, and probably moraine, which deflected the course of the river 

 slightly to the east. 



We must not lose sight of the fact that, however well established 

 the views Hess maintains would seem to be, there is a strong con- 

 sensus of opinion against the great erosive power with which glaciers 

 are credited, and in favour of river-erosion, even in the formation of 

 the Alpine valleys. M. E. A. Martel brings together a formidable 

 array of facts and authorities in support of his own judgment to this 

 effect. 1 Thus he notes that MM. Fabre, Boule, Schardt, D. Martiu, 

 Mazauric, &c., have demonstrated that many of our present valleys 

 existed prior to the Quaternary epoch. H. Schardt, writing of the 

 geological structure of the neighbourhood of Montreux, says : — " The 

 valleys have been dug out before the glacial epochs Warren Upham, 

 too, writes upon pre-glacial erosion in the course of the Niagara gorge, 

 and so forth. It would be out of place here to attempt even a 

 moderate discussion of this interesting physico-geological question; 

 but if we may venture to query the views of such eminent masters of 

 glacial geology as Penck, Briickner, Hess, &c., we may ask whether, 

 if the Yenter-Tal, Gurgler-Tal, and other such valleys had existed in 

 pre-glacial times, they might not have received their remarkable 

 structure with parallel rims from ice-action, continued for consi- 

 derable periods at different stages of glacier- decline ? It seems 

 unquestionable that many of the steep-sided gorges — some dry, others 

 occupied by small lakes, as that near Wesen, on the Zurich-Chur 

 railway-line — and ravines now being formed, owe their origin to 

 waters rushing from melting glaciers, rather than directly to glaciers 



^ "Spelunca," tome vi., pp. 511 et neq. 



