ANCIENT LAKES AND RIVER COURSES. 



551 



waters is ponded back, and spreads over the low lands between Stoke Edith and Here- 

 ford, and thus presents an exact picture of that state of things, which must have had a 

 long continuance in the earlier periods of the existing surface, before the channels near 

 the mouths of the rivers were sufficiently deepened to afford an easy exit to their waters. 

 The whole extent, indeed, of the flat country of the Wye around Hereford affords strong 

 evidence, that there was a period when the waters of the river, being partially dammed 

 up, produced a lake of great magnitude, which can have been reduced to a simple river 

 only, by the deepening of the gorges between Ross and Chepstow. 



Besides these evidences of lacustrine and broad river accumulations in Herefordshire, 

 and the adjacent parts of Salop and Worcester, the more mountainous regions of the 

 Welsh borders present many deposits of fine silt and shingle, the nature of which seems 

 to be best explained, by supposing the cavities in which they occur to have been occu- 

 pied by water, which was little agitated during long periods. In the vale of Radnor, for 

 example, there is now only an insignificant rivulet; yet its level surface, and the character 

 of its alluvium indicate, that it was long submerged. The appearances in the embayed 

 flat around the town of Presteign would also induce us to suppose, that the fine debris 

 with which it is strewed, was similarly accumulated. The Vale of Montgomery, though 

 encumbered in parts by coarse detritus from the adjoining hills, may also in great measure 

 have been covered with its present alluvium, by lacustrine waters collected from the 

 want of a ready egress of the Severn to the north, or of the Onny to the south-east 1 . 

 There are strong evidences, indeed, of a lacustrine deposit in a depression connected 

 with the Vale of Montgomery, and between the Long Mountain and the Cornden Hills, 

 filled as it is by a dense and deep clay with partial peat bogs, from which large trees 

 have been extracted. The drainage of this tract is now effected by the Camlet, a 

 sluggish, small stream, which, rising in the Shelve Hills, descends into the vale of 

 Bishop's Castle, where it divides ; the principal branch the Onny, running eastward 

 in the direction of the main or coarse gravel drift ; the other, bending back as it were 

 upon its former course, flows to the N.N.W. in a deep and narrow ravine called 

 Marrington Dingle 2 : it is afterwards deflected to the south and west by a low barrier, 



1 The basin-shaped form of the Vale of Montgomery and other similar depressions in Silurian shale or 

 mudstone, have led some persons to imagine that they might contain coal; and Mr. More of Linley bored many 

 yards through the superficial detritus between Bishop's Castle and Norbury. I need not here repeat, that there 

 is not the slightest chance of ever finding coal in the Silurian rocks, and therefore to penetrate gravel, merely 

 to reach such rocks, is indeed labour thrown away. (See pp. 328, 411 and 488.) 



9 The course of the Camlet through the fissure of Marrington Dingle, in a direction precisely the reverse of 

 the ancient lines of drainage, is a very striking proof of how this stream has taken advantage of one of the last 

 formed rents and depressions by which the surface has been modified. In following the thickly wooded banks of 

 this little stream from Church Stoke to the north-west, the traveller, who merely hears the gurgling of the 

 water, is impressed with the belief that he is ascending to its source, while in reality he is descending towards 

 its mouth. This deception is produced by the partial rise of the hills towards the north-west, though the 

 bottom of the valley really deepens in that direction. This added to the known fact, that the great drainage of 



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