50 



geologically coloured, on a scale of three inches to the mile ; 

 upon this is laid down the various superficial Gravel accumu- 

 lations, their ages being differentiated by coloured dottings, 

 which thus are made to express the distinctive character of 

 the drift, whether quartzose or oolitic, local or derived 

 from distant regions through the agency of water or ice. 

 Besides this, the map expresses in numbers the height of 

 almost every elevated point within the area refeiTcd to, so that 

 argument deducible from elevation is at once settled. The 

 heights have been determined by aneroid and trigonometrical 

 measurements. The questions of the formation of gravel, the 

 derivtition of the pebbles of which the gravels are composed, 

 the origin of boulders, &c., are all discussed in Mr. Lttct's 

 papers. Numerous sections of the gravels constructed from 

 the most important localities are given, shewing their manner 

 of accumulation, superposition, and arrangement done to scale ; 

 and shewing the variable thickness of the deposits at different 

 localities over the area treated of. 



The argument of the paper is based upon these sections which 

 in themselves pourfcray a marked history as respects arrange- 

 ment and accumulation. They are all carefully described in 

 Mr. Lucy's memoir, their fossil contents are noticed, and the 

 peculiarities, and source of the gravels comprised in them are 

 carefully described ; rocks that have travelled from the North 

 and North-West of England and Wales, from Derbyshire, 

 Lancashire, Shropshire, and other remote localities are detected 

 and approximately traced to their sources. The line of junction 

 of the " Northern Drift" gravels with the local Oohtic debris 

 in the Severn Yalley, and higher levels, have been laid down 

 and their modes of accumulation explained. The terraces of 

 river- gravels, forming low table-lands, rising from 40 to 100 

 feet above the present Severn, limiting, as it would appear, the 

 vertical distribution of Mammalian remains in this valley, are 

 carefully noted and described. Finally, the gravels known as 

 " Northern Drift" are traced to the height of 750 feet on the 

 Cotteswolds, thus incontestably proving the submergence of this 

 area some 800 feet during the Post-Pliocene Epoch. 



