Revieivs — Memoirs of the Geological Survey. 227 



as they deal with distinct areas and strata. While, however, the 

 district described by Mr. Topley has ever been a favourite field for 

 geologists, that into which Mr. Judd carried his observations had 

 been studied but very little previously, and he consequently has had 

 the benefit of recording more new facts, and of establishing the 

 relations of beds concerning which many erroneous opinions had 

 been previously entertained, 



I. — A now distinguished Professor of Geology once described the 

 structure of the Wealden area in the following pithy sentences : — 

 " Plutonic action has been very rampant throughout the Wealden 

 area, tossing rocks up and throwing them down, and twisting them 

 about in almost every conceivable manner. A few coloured sheets 

 of paper torn to pieces and then crumpled up and squeezed into a 

 solid mass, will give an adequate idea of their condition before they 

 were brought under atmospheric influences. If we cut valleys in 

 miniature out of the mass of paper, the coloured fragments exposed 

 in their sides will represent most accurately the disconnected surfaces 

 of the rocks, laid bare by rain, frost and the erosive action of the 

 streams." Such a chaotic mass of strata might be considered to 

 represent the structure of the Wealden area b}^ one who, without 

 any previous experience, attempted to unravel the geological struc- 

 ture of some of the many little complicated and faulted tracts that 

 are to be met with in this district ; but such is not the idea to be 

 gained from a study of Mr. Topley's very lucid account of the strata. 



The Hastings Beds especially are made up of a series of more or 

 less indurated sands and clays, many of the members of which are of 

 a local or impersistent nature ; and it is by no means easy, when, as 

 is frequently the case, numerous faults occur, to determine the precise 

 horizon of any bed of clay or sand. Nothing but the systematic 

 mapping of these beds could determine their position ; and how well 

 this has been done can be seen from a careful study of the Geological 

 Survey maps of the district. As an instance, the Tilgate beds of 

 Dr. Mantell have been shown to comprise beds on several diiferent 

 horizons. The Lower Greensand exhibits many local variations in 

 thickness, and in the character of the subdivisions that can be made 

 in it. 



Both Wealden Beds and Lower Greensand have been subdivided 

 by Mr. P. Drew, and his divisions have been established in the 

 Wealden district. 



This area is taken to inchide all the beds that are enclosed by 

 the Chalk escarpments of the North and South Downs, and the ranges 

 that unite them west of Farnham, Alton, and Petersfield. 



The strata described are therefore \hQ Upper Greensand, Gault, 

 Lower Greensand or Upper Neocomian, Wealden Beds, and the 

 Superficial Deposits. But this statement gives but a bare idea of 

 the scope of the work. The many subdivisions of these strata are 

 described in detail ; the gravels are treated in their relations to the 

 different streams and rivers ; while the Alluvium, Submarine Forests, 

 Blown Sand and Shingle are separately noticed. Physical Geology 

 has received much attention — the structure of the country, its scenery 

 and agricultural characters being described. 



