FLY-FISHER. 95 



which is Llyn-y-myngel, is neither more nor 

 less than a mountain tarn of rather more than 

 ordinary dimensions. The extensive range of 

 mountains which, is crowned by Cader Idris, 

 descends abruptly on the south east, into a gorge 

 which is the commencement of a long narrow 

 valley, down which the river Dysynni finds its 

 way to the sea. The lake is a more than usually 

 evident consequence of the laws which geologists 

 recognize wherever a lake exists, and nowhere, 

 perhaps, are the causes more clearly demon- 

 strated, nor could a geologist well find a more 

 apt illustration of the simple axioms by which a 

 lake has been originally formed. 



The same convulsiye force, probably volcanic, 

 which at a far remote period raised the bare 

 stern granite masses of Cader Idris to the clouds, 

 threw across this narrow valley a mound of rocks 

 (now covered with soil and verdure), which, about 

 two miles down its course, has arrested the cur- 

 rent of the streams from the upper valleys, and 

 suffering only one narrow exit to be worn by the 

 waters, keeps them back in the hollow of the valley 

 at a certain level, and forms the lake. So com- 

 pletely does the lake cover all the level ground, 

 that only at its head, where, as usual, the delta 

 formed by the gradually subsiding debris from 

 the mountains has given a few marshy meadows, 



