Philip Lake — Bala Lake and Hirer System. 243 



4. Valley of Tal-y-llyn and the Towyn Eailway. Nearly in 

 line with this, but apparently quite disconnected, is the "Valley 

 of the Dee between Llandderfel and Corwen, and the valley of 

 Nant Morwynion. 



5. Afon Dyfi up to Cemmaes, and perhaps to the source of the 

 river. 



6. River Banw from Llanfair to its junction with the Vyrnwy; 

 then the Vyrnwy to its junction with the Tanat. The rivers Ceiriog 

 and Dee below Chirk perhaps belong to this valley. 



7. River Severn from Llanidloes to its junction with the Tanat. 

 Among the smaller valleys belonging to this system are (a) Cwm 



Prysor and Afon Tryweryn above its junction with Afon Gelyn, and 

 (h) a small part of the Vyrnwy below the Liverpool Waterworks, 

 River Marchnant, River Ceiriog from Llanarmon Dyflfryn Ceiriog 

 to Llansantfifraid Glyn Ceiriog. Other shorter valleys of similar 

 character and direction undoubtedly exist, but these I have made 

 no attempt to indicate. 



A closer examination would certainly reveal more clearly the 

 connection and continuations of some of these valleys ; but enough 

 is shown upon the map to prove that some at least of these lines 

 of valleys are continued, with little or no interruption, for great 

 distances. 



That these valleys have exercised a profound influence upon the 

 drainage of the country is quite clear, and most of the principal 

 rivers lie in them. They cut up the country, more or less 

 completely, into parallel strips ; and the drainage of each strip 

 is intercepted by one or other of these parallel valleys. In the 

 most northerly strip, between the Menai Straits and Traeth-bach, 

 most of the streams flow northwards. But in the others the 

 greater part of the drainage of each strip falls into the valley lying 

 south of it ; while the streams which run northward are generally 

 small and unimportant. 



For instance, entering the valley of the Bala fault from the north, 

 we have Afon Eden, Afon Lliw, Afon Llafar, Afon Tryweryn, the 

 Ceirw, and the Alwen ; while from the south, the most important 

 is Afon Twrch in Cwm Cynllwyd. 



The question then arises, Avas the drainage of each strip estab- 

 lished independently, after the formation of the long valleys ; or 

 was the drainage established first, and the long valleys formed 

 afterwards ? In the former case there would, presumably, be no 

 connection between the streams of adjacent strips ; in the latter, 

 we should expect the more important streams of one strip to have 

 their representatives in the next. 



Beginning with the streams which flow into the valley of the 

 Bala fault from the north, we have first Afon Eden, with its 

 tributary Afon Mawddach.' This important river runs southward 

 till it enters the Mawddach estuary at Llanelltyd, where it turns 

 suddenly almost at right angles. But if we continue the line of 



^ After the juuctiou of these two the river is called the Mawddach. But the 

 Eden is clearly the priucipal branch, inasmuch as it maintains its direction unchanged. 



