888 



THE ]ÎRITISII ISLES. 



large a scale as in tlic mouutains bordering upon the Adriatic. Sometimes it 

 happens that the arch which covers one of the corroded hollows or channels gives 

 way, and the chasm thus created may give birth to a lake, or lay open an under- 

 ground river channel. It is thus that Lough Lena feeds both the Dell, a visible 

 atHuent of the Boyne, and an underground channel which communicates with a 

 river flowing into Lougli Eee. The great Lough Mask, Avhich fills a rock basin 

 in Connemara, has apparently no outlet, except through an artificial canal connect- 

 ing it with the still larger Lough Corrib. But on closer examination it has 

 been found that it is drained by an underground river, which reappears in copious 

 springs at Cong. These springs, which immediately give birth to a large river, 



Fig. 196.— The Underground Emissary of Lough Mask. 

 Sccole 1 : 145,000. 



S-ao^Wo+Gr. 



. Miles. 



were formerly held in high veneration, and an abbey was built by their side. 

 Several lakes, similar in all respects to that of Zirknitz, in the Carso, are to be 

 met with in the fissured limestone region of Western Ireland. During summer 

 they retire into underground cavities, and sheep browse upon the herbage which 

 sprino-s up on their bed ; but soon the rainfall causes the hidden water to rise again 

 to the surface, the lake bed is once more filled, and sometimes it even overflows 

 and inundates the country around. One of the turloughs, or winter lakes, of 

 Galway occasionally expands until it is 2 miles wide.* 



But whilst some lakes, owing to the erosive action of the water, are perpetually 

 *- Willi im Hughes, " Geography of the British Islands." 



