SILURIAN DRIFT FROM NORTH-WEST TO SOUTH-EAST. 



strewed sometimes with bowlders, coarse gravel and clay* at others with finely com- 

 minuted materials, the whole, however, being invariably of local origin. Much of 

 the coarse detritus is lodged upon the western limits of the Old Red Sandstone, and 

 is found always in situations where the bowlders may be traced, within the space of 

 a few miles, to their parent rocks. Thus, for example, in the neighbourhood of 

 Kington, the large blocks of syenite, hypersthene rock, or other varieties of trap, and 

 of Cambrian, or Silurian Rocks which are strewed over the surface, have been rolled 

 off from the adjoining hills of Old Radnor, a tract which has been shown to have 

 been formerly much subject to volcanic action, (PI. 33. f. 4.) whilst in the finer 

 gravel are found many of the well-known fossils of those associated Silurian rocks, 

 which here dip under the Old Red Sandstone. Wherever there have been violent 

 elevations of the strata, we invariably find these accumulations thickly spread out, 

 obscuring the junctions of the various deposits. Striking examples occur, along the 

 outline of the Silurian rocks, from the Ludlow promontory and the gorge of the Onny 

 to the environs of Kington. To the south-west of Kington the lower beds of the 

 Old Red Sandstone, resting upon the slopes of the Ludlow rocks, have been the sub- 

 aqueous water-shed, down which the coarse detritus has been swept, and thenceforward 

 to the south-western termination of these groups, their junctions being free from such 

 detritus, are clearly defined. In the neighbourhood of the Hay and facing one of the 

 chief transverse gorges of the Wye, mounds of coarse rubbish are piled up against the 

 escarpment of the cornstone or middle group of the Old Red Sandstone. On the rising 

 grounds between Hay and the Sarnesfield Hills, the surface of the lower beds of the Old 

 Red Sandstone is loaded with this coarse drift, which renders whole parishes arid, as 

 indicated by the appellations of "Rough Moors," "Labour in Vain," &c. This de- 

 tritus may strictly be termed local, either being made up entirely of fragments of the 

 lower beds of the Old Red Sandstone itself, or derived from the adjacent Silurian rocks, 

 whose frontier is distant only five or six miles. So local, indeed, is this detritus, that 

 it has not even travelled down the slope of these hills into the rich contiguous valley of 

 Weobly, still less has it been carried to the escarpment of the cornstone of the Old 

 Red Sandstone, though these situations lie exactly in the line of the drift. In passing 

 to the south-east, in proportion as you recede from this frontier of Silurian rocks the 

 coarse bowlders disappear, and the gravel becomes more and more finely comminuted. 

 At Luston, near Leominster, and two miles from the boundary of the Silurian rocks, 

 the following section may be observed in one of the gravel pits. 



1. Red stiff loam. 2. Fine reddish sand. 3. Sand and pebbles of Silurian rocks, quartz, trap, &c. irregularly bedded. 

 4. Fine red sand. 5. Strong coarse gravel made up chiefly of fragments of Wenlock and Ludlow rocks, with many of their 

 included fossils. 6. Fine white sand. 7. Fine red sand. 8. Fine sand with. small pebbles. 9. Coarse red sand. 10. Sand 

 with bowlders of Silurian rock, some as large as eighteen inches by four, so little rolled as to preserve the sharpness of their 

 edges. 



This section, with many others along the escarpment of the cornstone formation, 



