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constitute what has been called ''diluvium" in other parts of England; 

 all the loose materials in S. Salop, Herefordshire, and the adjoining 

 Welsh counties having been derived from the Silurian and trap rocks 

 of the adjacent mountains. These mountains range from N.E. to 

 S.W., presenting inclined planes to the S.E., on the surfaces of 

 which the broken materials are distributed. Four of the rivers which 

 descend from the higher parts of Wales flow to the S.E. in accord- 

 ance with the prevailing lines of drift, traversing the ridges of Silurian 

 rocks through fissures which have resulted from dislocations of the 

 strata. These are the Teme, the Onny, the Lug, and the Wye, all 

 tributaries of the Severn. That great river, on the contrary, does not 

 follow the " line of drift" to the S.E., but escapes from the mountains 

 to the north by a lateral gorge under the Breidden Hills ; and after 

 a circuit in the Vale of Shrewsbury passes eastward through a narrow 

 transverse rent in the upper Silurian rocks and coal measures of Coal- 

 brook Dale ; and taking its final course southward, from Bridgnorth 

 to the Bristol Channel, forms the eastern limit of the country covered 

 by the Welsh or Silurian detritus. The drainage of the Teme, Onny, 

 Lug, and Wye, is described in detail, with a view of showing, that in 

 the valleys in which these rivers descend from the mountains, the ma- 

 terials change with each successive ridge, the larger fragments being 

 transported only short distances ; and that as the gravel advances into 

 the plains, it becomes more finely comminuted ; Herefordshire and 

 the low countries being chiefly covered with local debris of the old 

 red sandstone. The author specially distinguishes this drift, which is 

 extensively spread over valleys and slopes, and sometimes found in 

 high situations, from the detritus which has been carried down by rivers 

 under the atmosphere, conceiving that the former accumulations have 

 been washed down the surfaces of the inclined strata ; because wherever 

 the latter dip to the S.E., so are the materials invariably found to have 

 been propelled in that direction. In no instance has any fragment 

 been found on the west which can have been derived from rocks on 

 the east. He therefore believes that at those periods when the Silu- 

 rian and older rocks were raised from beneath the waters, great 

 quantities of coarse and fine detritus were drifted down these slopes j 

 and that as the rocks on which the loose materials have been depo- 

 sited are replete with dislocations, and penetrated at many points by 

 ridges of trap rock, it is to be inferred, that during and after the 

 evolution of this volcanic matter, great and successive elevations of 

 the bottom of the sea took place, throwing up the drifts to the various 

 heights at which we now find them. As soon as the land was raised 

 from beneath the sea, the present rivers, it is conceived, began to flow ; 

 passing through the ridges by gorges produced by great lateral cracks 

 the result of elevation ; and that these streams have since merely trans- 

 ported to short distances those broken materials which were previous- 

 ly gathered together by subaqueous drift. To prove that the drifted 

 matter of each district within this region may be referred to disturb- 

 ances purely local, it is shown that although wherever the hills have 

 been elevated from N.E. to S.W. the lines of drift are from N.W. to 

 S.E., yet in those contiguous tracts which have been elevated in other 



