208 THE RIVER VALLEYS OF SOUTH-WEST IRELAND. 



tinually flooded with water, and during this time the 

 clays, alluvium, &c., were deposited over the peat. 

 Because a bog containing trees, &c., may be found 

 inside and outside a sea-beach, it has been argued 

 that the trees may have grown at their present level, 

 while since then the sea has moved its beach in land- 

 wards, exposing the bog and trees to seaward. The 

 fallacy of this reasoning is easily exposed if we only 

 examine into the conditions under which the trees 

 found would grow ; as oak and most other trees can- 

 not be grown except on drained land, which could 

 never exist naturally in places below high-water 

 mark. 



