550 



ANCIENT LAKES DRAINED BY TRANSVERSE GORGES. 



the gorge of Aymestry, and at the same time choaked it tip with this coarse detritus, 

 which was thus one of the immediate causes of the formation of the Wigmore Lake. 



The Lugg prevented by the escarpments near Lingen from continuing its south- 

 easterly course is, indeed, deflected to the E.N.E. until it reaches the Aymestry gorge, 

 through which it escapes into the plains of Herefordshire ; while it is completely cut off 

 from all communication with the Wigmore Lake by the high mounds of ancient gravel 

 above adverted to, and also by the undulating form of the subsoil. Not so with the 

 Teme, for the same movements of elevation which raised the Ludlow promontory, and 

 heaped up the detritus in the gorge of the Lugg, doubtless also produced the fissure 

 by which the Teme issues into the low country ; leaving it, however, unencumbered 

 by any coarse drift. This fissure, which in earlier days, could with difficulty have af- 

 forded a passage to its waters, must (judging from the present rapidity of this river in 

 floods,) have been subsequently so much deepened, as to complete the drainage of 

 Wigmore Lake and Leintwardine Bottoms. Of this, indeed, there can be little doubt, 

 since it is well known that within the period of history a large portion of the " Wigmore 

 Lake" (the name by which it is still known) was a mere profitless marsh, the super- 

 fluous waters of which have since been drained off through the channel of the Teme. 



In its course to the east, the Teme offers another example of having been barred up, 

 and of having given rise to a lake, lower than that of Wigmore. To the east of the town of 

 Tenbury, finely laminated alluvia form low terraces, about twenty feet above the present 

 bed of the river. These materials appear to have been accumulated under tranquil water, 

 and the form of the depression supports the hypothesis ; for the whole of the valley 

 between Tenbury and the Abberley Hills, might even now be suddenly converted into 

 a lake, by merely shutting up the gorge of Knightford Bridge, the only transverse 

 fissure in the chain of Silurian hills extending from Malvern to Abberley, through 

 which the waters of the north-west part of Worcestershire and the north-east of Here- 

 fordshire can find their way into the valley of the Severn. (See Map.) 



It is to be presumed, indeed, that many of the rivers which now pass through gorges 

 to the south-east, from the Welsh mountains on the north-west, must, when fiuviatile 

 action commenced, have been flooded back, and have caused lakes ; for we cannot 

 examine the finer detritus spread over the flats and basin-shaped cavities in which the 

 Wye, the Onny, or the Lugg meander, without attempting to explain the phenomena 

 in this manner. The low lands around the town of Hereford, particularly where the 

 Lugg empties itself into the Wye, offer one of the clearest examples in the drainage 

 of this region, where such sheets of water must have had a character intermediate 

 between fiuviatile and lacustrine. Deep red silt and clay, the detritus of the marl of 

 the Old Red System, here constitute to a great depth a wide area of low and fertile land. 

 That this sediment was carried down during many ages by the Lugg, may be well ima- 

 gined on inspecting that red and turbid stream, when flooded. It empties itself into 

 the Wye at so low a level, that when swollen by heavy rains, the great volume of its 



