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I.—Bala Lake and the River System of North Wales

Published online by Cambridge University Press:  01 May 2009

Philip Lake
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Extract

In North Wales there are several valleys which run parallel or nearly parallel to the valley of the Bala fault, and, like it, are crossed by watersheds which are quite inconspicuous. One of these watersheds separates the head of Cwm Prysor from the source of Afon Tryweryn; a second parts the springs of the Conway from those of Afon Dwyryd; and a third divides the waters of Nant Ffrancon from those of Afon Llugwy (a tributary of the Conway). (Pl. XI.)

Type
Original Articles
Information
Geological Magazine , Volume 7 , Issue 6 , June 1900 , pp. 241 - 245
Copyright
Copyright © Cambridge University Press 1900

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References

page 243 note 1 After the junction of these two the river is called the Mawddach. But the Eden is clearly the principal branch, inasmuch as it maintains its direction unchanged.

page 244 note 1 It will be noticed that this line is almost exactly parallel to the general trend of the coast of Cardigan Bay, a fact which seems to point to some community of origin.

page 244 note 2 If the radial valleys existed before the formation of the transverse valleys, we might expect that where the lines joining the remnants of the radial valleys cross the intervening ridges, there should be a col or depression ; and this is, indeed, very commonly the case. Moreover, opposite each important stream where it enters a transverse valley, there is generally a little valley running down from the col and entering the transverse valley on the opposite side. For example, opposite the point where Afon Lliw enters the valley of the Bala fault, a valley runs in from the col called Bwlch-y-pawl, which is situated at the head of the River Vyrnwy. Opposite Afon Tryweryn is the valley of the Hirnant, and from this we pass across a col into the head of Afon Tanat. Similarly, in the line of the Ceirw we find Afon Trystion entering the valley of the Dee from the opposite side ; and from the head of Afon Trystion a decided depression leads us to the head of the Ceiriog.