506 MESSRS. ARNOLD-BEMROSE AND DEELET ON [Aug. lSg6 r 



clays of the area. The patches of boulder-clay now remaining are 

 merely portions, which denudation has spared, of great sheets which 

 once nearly filled the lower grounds of the Trent Basin. 



The alluvial plain through which the Trent, and the lower 

 reaches of many of its tributaries, run, consists of a thick bed of 

 gravel, for the most part covered by a layer of brick-earth. Sec- 

 tions have been opened out in it at many points. 



An excavation, for a gasometer, to the east of the Midland Rail- 

 way Station, Derby, passed through brick-earth and then gravel and 

 sand. Limestone and gritstone were plentiful. A few flints were 

 seen. The deposit was regularly stratified, and false-bedded, and 

 quite undisturbed, nothing in the nature of ' trail ' being seen at or 

 below the surface. 



The ballast-pit (now full of water and known as Trent Lake) 

 exposed a fine section of modern Trent gravel. Here also the 

 ' trail ' was absent, the upper surface being quite undisturbed and 

 the gravel, sand, and brick-earth regularly stratified from the brick- 

 earth to the bottom of the gravel. 



At Colwick, near Nottingham, another pit exposed these modern 

 gravels. Here the brick-earth was about 2 feet thick. The surface 

 showed no trace whatever of disturbance, and the gravel and sand 

 were well stratified and false-bedded. 



In all cases where the newer deposits have been exposed in 

 section, ' trail ' and ' underplight ' were quite absent, the surface 

 portions being quite free from contortions. The low-level gravels 

 of course show signs of root-penetration, the sand and pebbles being 

 bleached or discoloured by the action of organic acids, etc., but this 

 cannot be confounded with ' trail/ neither can the subsidences 

 resulting from the action of underground denudation. 



Certain physical features of the valleys also deserve notice. 



Wherever the modern alluvial plain is bounded by a high-level 

 gravel- terrace, or other resisting rock, the boundary-line between it 

 and the alluvium is marked by a steep escarpment. Such a con- 

 tinuous low cliff may be traced through Derby, Alvaston, Elvaston, 

 Aston-upon-Trent, Weston-upon-Trent, and thence along the north- 

 ern side of the Trent Valley as far as Egginton. It then turns up the 

 Dove Yalley. It may also be traced up the Trent Valley beyond 

 Burton. 



On the northern side of the Derwent Valley the escarpment is 

 continuous between Borrowash and Long Eaton. Passing down 

 the Trent it commences again at Beeston, and on the right bank of 

 the river it may be traced from Gamston in the direction of Newark. 



Where streams enter the main valley, the terraces are breached, 

 and the brooks run in V-shaped hollows. 



These escarpments separate the disturbed from the undisturbed 

 deposits, the high-level formations only showing the ' trail/ 



At one time, no doubt, the two upper terraces at Weston-on-Trent 

 (Quart. Journ. Geol. Soc. vol. xlii. 1886, p. 469) faced the river 

 with steep slopes also, but their edges have in some way been 



