SILURIAN DRIFT FROM NORTH-WEST TO SOUTH-EAST. 513 



indicates a method of accumulation precisely analogous to that in which gravel, sand, 

 and bowlders are now heaped together on sea shores or in estuaries ; while the change 

 in the nature of the drifted materials proves that the currents which propelled them, 

 flowed from the north-west. 



Advancing from the Welsh frontier and passing to the south-east, even the fine gravel 

 of the Welsh and Silurian Rocks disappears, and before we reach the central and eastern 

 parts of Herefordshire, the surface of the rich red marls is, for the most part, free from 

 all transported matter. 



This arrangement of the coarse gravel on the north-west, and fine towards the south- 

 east, demonstrates, that the drifts which affected the surface of the great trough of 

 Herefordshire proceeded from the former direction. When we attentively examine 

 these heaps of gravel, we find, however, that the more finely comminuted varieties, 

 alternate so often with sand, and are so different in composition, that we cannot but 

 attribute their deposit to long-continued periods of subaqueous accumulation, and not 

 to any sudden transitory rush of waters. The plain between Leominster and Aymestry, 

 being so near an important elevated mass, the Ludlow promontory, is, as we might 

 suppose, much encumbered with this detritus, and similar heaps are lodged at various 

 heights upon the edges of the cornstone escarpment in the neighbourhoods of Tenbury 

 and Leominster. These accumulations are by no means confined to the vale, like the 

 example cited at Luston, but are equally spread out in high situations, where no 

 streams can have flowed since the present configuration of the land, and also on the 

 sides of low, broad, valleys, through which the principal rivers pass from the north- 

 west to south-east. 



In ascending any one of the transverse valleys, beyond the limits of the Old Red Sand- 

 stone, the distribution of the coarse and fine detritus also shows a similar transport from 

 north-west to south-east. That this has invariably been the direction of the currents 

 throughout the country under review is proved, by never detecting fragments of the 

 rocks which lie to the south-east in any part of the north-western region, all the broken 

 and drifted materials being lodged to the south-east of each particular ridge, and never 

 to the north-west. 



Let us first look to the valley of the Teme. This river has its source in the high 

 lands of Kerry Hill, west of Knighton, to which place it glides down through the soft 

 sandstone and flag of the Ludlow rocks. In all that high region, there is not a bowlder, 

 which cannot be referred to some rock upon the west and in the immediate vicinity. 

 Whatever is the composition of the small shingle or modern alluvia carried down by 

 this stream, such are the alluvia of ancient date, though the latter are coarser and placed 

 at higher levels on the mountain sides. Let the reader specially dwell upon this im- 

 portant fact. 



Again, the Onny, a tributary of the Teme, presents similar phenomena, accompanied 

 by still stronger proofs of the agency of a body of water no longer in action. This sluggish 



