THE LAKE-BASINS OF lARCONNAUGHT. 113 



formed the bar and lagoon. This is probably correct, 

 as it must be borne in mind that at no very remote 

 period all the streams and rivers in larconnaught were 

 larger than they are now, as two or three hundred years 

 ago most of this area was a forest. Boussingault, 

 who wrote on this subject, gives facts showing the 

 effects caused by the cutting down of the forests on 

 the streams and springs in South America ; further- 

 more, this fact is so well known on that continent, 

 that some of the South American governments have 

 passed laws regulating the felling of timber. 1 



Other evidence in favour of the larconnaught 

 streams having been larger than they now are, is 

 that in different places peat is gradually growing 

 over and filling up old stream-courses. 



If a stream debouches on an open seaboard, a 

 bar and lagoon may form if the ground is low and 

 the volume of water discharged is insufficient to sweep 

 away the sand driven up by the wind and sea. Such 

 lagoons were remarked on the coast of S.W. Mayo, 

 but more extensive ones are found in South-east Ire- 

 land. These, such as that which existed at Kilmore, 

 County Wexford, are separated from the sea by irre- 

 gular eskers (anglice, ridges) of more or less fine, often 

 stratified, sand. Such eskers are evidently, in the first 

 place, bars formed between the open sea and the 

 shoal water, which afterwards are augmented by sand- 



1 Edinburgh Phi/. Jour. xxiv. (1836), pp. 89-91, and 102, 103. 



H 



