462 J. Prestvvich, Esq., on the 



Beds of coarse gravel and sand, formed apparently by the junction of the 

 two foregoing divisions, abound in the valleys and on many of the hills from 

 Bridgenorth to Lilleshall, accumulating in great thickness in some valleys, as in 

 Willey Park, in Lightmoor Old Park, New Lawley, and AVoombridge. Al- 

 though it ranges over several hills, attaining, as does the sand, a height of 700 

 feet above the level of the sea, still the summit of many of the hills and the 

 surface of a few valleys are free from it. The thickest deposits are in the 

 valleys running from the lowlands westward of the coal-field, as Muxton, 

 Oaken Gates, Ketley, New Dale, New Lawley, and Build was. Eastward of 

 the coal-field, it abounds over the new red sandstone, especially through the 

 parishes of Sutton and Brockton. The rapid variation in the thickness of 

 this deposit is everywhere remarkable. At Hills Lane, where the ground, 

 although high, is level, the thickness in one place is more than 90 feet, whilst 

 100 yards distant it is only 7 feet. It is frequently found to be 50 to 60 feet 

 thick, as at Willey, Lightmoor Park, in places near New Lawley furnace, 

 Ketley, Woombridge, New Hadley, and Donnington. A good instance occurs 

 in the valley extending from New Hadley to the Oaken Gates. Near Woom- 

 bridge church the Ketley fault throws up, to the eastward, the lower series 

 of the coal-measures, the strata cropping out successively on the sides of the 

 hills, leaving the lower coal-beds in the valley; but owing to the deep and 

 extensive denudation in this valley, the coals are frequently removed, and at 

 other places are immediately overbed by the gravel, and cannot in consequence 

 be worked. The denuding action of the water has here worn a deep and 

 precipitous channel, on the north side of which the truncated coal-measures 

 being cut off almost vertically, the gravel filling the channel acquires, in a 

 few yards, a thickness of above 100 feet. 



It thus appears that the drift has accumulated principally in valleys, hollows, 

 and narrow channels, but that it spreads occasionally, in decreased thickness, 

 over the high grounds*, materially modifying or leveling the more consider- 

 able irregularities of surface. 



Marine shells of recent species are occasionally found in tlie upper gravel. 

 Amongst them are specimens of an Ostrea and of a spiral univalve much 

 broken, but apparently of the genus Turritellaf. 



* The frequent occurrence of this drift interferes greatly with the examination of the surface 

 rocks, preventing, in the more level districts, any natural sections from being exhibited. 



f In Mr. Murchison's account of this drift in its extension over Salop, Cheshire, Worcester- 

 shire, &c., the Buccinum reticulatum, Dentalium entalis, Liltorina littorea, Tellina solidula, Car- 

 dium tuberculatum, Cyprina Islandica, Turritella ungulina, with fragments of Venus, Astarte, and 

 Donax, are stated to have been found in this gravel ; and amongst the localities quoted is one 

 near Wellington. See Silurian System, p. 533. 



