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PROCEEDINGS OF THE GEOLOGICAL, SOCIETY. 



chalk to the west of Petersfield. It is important to remark that in the 

 longitudinal parallel valley of Gault-clay (see fig. 3), as in the deepest 

 part of the Weald-clay valley, there are no accumulations of drift. 

 Several also of the long slopes of the Lower Greensand are exempt 

 from it. The debris is, in fact, more seen on the summits of the hills 

 of that formation, whether they be 50 or 300 feet above the level of the 

 present drainage ; and in all such situations the surface of the rock has 

 been powerfully eroded, and the flints lodged in its eroded cavities. 

 We must also recollect, that the summit of Rogate Common is much 

 higher than the opposite plateau of Malm Rock or Upper Greensand, 

 which has been so clean swept of all such fragmentary matter (see 

 fig. 3). In all these facts I can only recognize the results of an 

 agency of vast intensity, and clear proofs of a great force that drifted 

 the flinty materials in this district from west to east. 



To the east of the tract ranging from Petersfield to Midhurst and 

 Petworth, the reader may see, on reference to the Ordnance Survey, 

 how the elevations of the Weald-clay between West Grinstead and 

 the gorge of the Arun must also necessarily have arrested large por- 

 tions of these materials in the manner already described. We may 

 therefore, I repeat, suppose that a current translated this debris and 

 swept generally along from west to east, gathering fresh materials 

 from the harder parts of the subsoil over which it passed, and that it 

 traversed promiscuously low hills and dales, in this case along the 

 chief line of the existing drainage, but at great heights above its pre- 

 sent level. 



Other facts favour the inference, that a former powerful but trans- 

 ient current denuded the surface of the bare rocks in many parts, and 

 at the same time distributed broken materials along a zone of limited 

 width, and, on the whole, in a depression between the Chalk Hills 

 of the South Downs on the one hand, and the central ridges of 

 the Lower Greensand and Weald on the other. The escarpments of 

 the Chalk, extending from Butser and Buriton Hills on the west to 

 the Arun on the east, are nowhere broken in upon by any transverse 

 split, not even by any depression. Throughout this space the Chalk 

 with flints or Upper Chalk is so much thrown over to the south, that 

 no flinty bands now in situ are anywhere within the influence of 

 waters, which, having reference to the existing outlines, could trans- 

 port any materials from them into the valley on the north. In truth, 

 the whole of the escarpment between Butser Hill and Duncton Hill* 

 (the former 872 feet above the sea) is clearly exposed in all its parts, 

 with the Grey Chalk rising from beneath the White Chalk, and on 

 few portions of it, or of the broad plateaus of Upper Greensand and 

 valleys of Gault which lie to the north, are any flints visible. The 

 respective rocks are everywhere near the surface, and void of any 

 quantity of debris, as shown in fig. 2f . In the westernmost tract, 



* See Map of the Government Survey, and Section, fig. 2. 



f At Harting, near Petersfield, there is, indeed, strong reason to believe that 

 the Chalk has undergone a special amount of degradation at no remote geological 

 period ; for the most remarkable projection of that formation is there seen in the 

 peninsula (almost an outlier) called Tarbury Hill, which exposes the chalk-marl, 



