Vol. 62.~] THE CLAY-WITH-FLINTS. 149 



fragments, but nothing was found that could be mapped as Clay- 

 with-Flints, except a few patches near Wilsford and Woodford. 

 Now, if this material is mainly a Chalk-residue, how can its absence 

 on this part of Salisbury Plain be explained ? If, on the other hand, 

 it is mainly an Eocene residue, we should not expect to find it far 

 below the level of the basal Eocene plane. 



Within the area of Sheet 298, besides the few small patches above 

 mentioned, a long tract of Clay-with-Flints caps the ridge which 

 lies between the valleys of the Wily and the ladder, pointing 

 eastward to another patch on the slope of the hill north-west of 

 Salisbury ; and there are other spreads of varying extent in the 

 southern part of the district. 



The relations of these tracts of Clay-with-Flints to the tectonic 

 structure of the country are interesting and suggestive. The ridge 

 between the Wily and the N adder is capped by red and brown Clay- 

 with-Elints for a length of 9 miles, and it lies over the central axis 

 of a syncline which intervenes between the anticlines of the Vales 

 of Wardour and Warminster. It is, therefore, probable that the 

 base of the Eocene lay not very far above the summit of this ridge, 

 and that very little chalk has been removed from the watershed in 

 post-Eocene times, either by solution or by any other process. The 

 presence of the Clay-with-Flints here is quite comprehensible if it 

 is mainly an Eocene residue, but is inexplicable on the Chalk-residue 

 hypothesis. 



It may be mentioned that the western end of this tract of Clay- 

 with-Flints rises to a level of 700 feet, and that CI ay pit Hill on 

 the other side of the Wily valley, north-east of Codford, is capped 

 by a patch of materials (mottled clay and sand) which, although 

 disturbed, are recognizable as remnants of Reading Beds. 1 This 

 outlier probably owes its preservation to its having been let down 

 into a hollow in the Chalk, or to an ancient landslip. Its present 

 summit is only 586 feet above Ordnance-datum, but it suffices to 

 show that Reading Beds lay over this area at some level between 

 600 and 650 feet. 



The materials derived from the Reading Beds are here overlain 

 by a peculiar deposit, consisting of yellow sandy clay full of angular 

 flints and small quartz-pebbles, which is described by Prestwich 

 as extending along the ridge of Codford Hill, but is not shown on 

 the Geological Survey -map. Such a deposit seems to resemble 

 the Plateau-Gravel of .Berkshire more than the Clay-with-Flints, 

 although it may be a contemporary variation of the latter. 



How the flexures above mentioned are continued eastward is not 

 certain, except as regards that of the Yale of Wardour, which is 

 cut off obliquely by a fault striking roughly from west-north-west 

 to east-south-east. The intermediate syncline seems to be deflected 

 southward, so as to pass below Wilton and Salisbury, and may 

 possibly be continued into the syncline of the Eocene tract at 

 Alderbury. The Wily anticline appears to be prolonged to Lower 



1 See Prestwich, Quart. Journ. Geol. Soc. vol, xlvi (18S0) p. 144, and Greol. 

 Mag. 1898, p. 412. 



