416 J. Prestwich, Esq.j on the 



and diversified, and gradually decreases in altitude as it recedes from the 

 older rocks ; but to the north and north-west, the higher platform of the coal- 

 measures descends rapidly into the lowlands of the new red system. 



At Watling- Street, near Wellington, commence the lofty igneous axes of 

 the Ercal and Wrekin, Steeraway and Maddox, which constitute the boundary 

 in this portion of the area, and separate the coal-measures from tlie new red 

 sandstone. 



On the south-west no physical feature bounds the district ; but the reader 

 may supply this deficiency, by drawing a line from the end of the Wrekin to 

 Wenlock Edge, and thence to Bridgenorth. 



Having: thus defined, «enerally, the limits of the districts, I will describe 

 briefly, the principal physical features within them. 



The Severn divides the area into two unequal portions. Where it enters 

 the district from the west, it traverses a valley in (he Caradoc sandstone, one of 

 the Lower Silurian rocks ; it then passes through a narrow and beautiful valley 

 of Wenlock shale, flanked on the north by the hills of Little Wenlock and 

 Sunnyside, and on the south by the finely wooded and precipitous escarp- 

 ments of Wenlock Edge, Gleedon Hill, Tickwood Hill, and Benthall Edge. 

 Near Coalbrook Dale the valley rapidly contracts, and the Severn enters a 

 deep and narrow gorge in the Wenlock limestone, separating Benthall Edge 

 from Lincoln Hill. This gorge passes immediately into the coal-measures, 

 and intersects them for about two miles, to Coalport. A little beyond that 

 point, the river turns southward, and is bounded on the left by an escarpment 

 of new red sandstone, and on the right by hills of coal-measures, as far as the 

 Wren's Nest, beyond which it flows through precipitous ridges, wholly com- 

 posed of the new red system. Between Coalport and Bridgenorth the hills 

 are beautifully wooded, and intersected by numerous glens. To the south of 

 the Severn, the country is so traversed by deep valleys and ravines, that, with 

 the exception of Wenlock Edge, no connected ridge of hills can be traced. 

 The leading features, however, are, the fine and bold escarpments of Wen- 

 lock and Benthall Edges, and Sherlot Hill, which, rising to the height of 731 

 feet, constitutes the greatest elevation of the coal-measures, in this portion of 

 the field. To the north of the Severn, the surface is less generally broken, 

 the part occupied by the coal-measures, presenting an elevated and undulating- 

 outline, which averages about 400 feet above the level of the sea, or 300 feet 

 above that of the Severn at the Iron Bridge. Tlieir greatest elevation is 

 746 feet. The most prominent features in this portion of the field are the 

 Wrekin, which rises to the height of 1320 feet above the level of the sea, and 



