THE LAKE-BASINS OF IARCONNAUGHT. Ill 



driven up on to it by the sea, till eventually it be- 

 came a mound across the end of the bay, forming 

 behind it a fresh-water lagoon. The remains and 

 sites of similar bars and lagoons have been observed 

 in different places in the neighbouring glens, prin- 

 cipally at about the 350 feet contour-line which is 

 supposed to mark the margin of the sea during the 

 " Esker sea " period. The relations between the bar 

 and lagoon at Cleggan, and the remains in the glens, 

 will appear from their descriptions. 



On the north end of the Cleggan bar the sea acts 

 with the least force, consequently the embouchure of 

 the lagoon is there situated; naturally the drain- 

 age ought to be at or near the centre, where the bay 

 is deepest, but in that place there is only an under- 

 drainage when the tide is out. If, however, the land 

 rose, this drainage, which at present is a soakage 

 through the sand and gravel, would be continuous, and 

 gradually increase, till eventually it sapped the bank 

 and formed an open through it, which the stream 

 would deepen more and more, till eventually there 

 was a cut down to the bottom of the gravel mound. 

 If the gravel had accumulated in a simple bar, 

 it is probable all the water would be drained out of 

 the lagoon, and form a more or less level plain ; but 

 if there had been gravel mounds formed in the ground 

 behind the bar, the bottom of the lagoon would be 

 uneven ; and probably, after the water had cut a new 



