PLIOCEN-E PERIOD IK EIT^LAKD. 481 



Over the region of formations older than the Pliocene the extent 

 to which this denudation has occurred is in most cases not to be 

 gauged, by reason that so much denudation had preceded this which 

 we are now considering ; but in Sheets 68, 67, 66, and parts of 48 

 and 50, or in those parts at least of them where the Chalky Clay in 

 great thickness has not masked the preceding formations, we can 

 perceive the way in which this denudation has acted upon the 

 formations accumulated during stages I. and II. It was in this way, 

 therefore, that, as the sea-bottom rose, the Contorted Drift became so 

 much denuded and separated into detached portions, such as those 

 shown in fig. I., the spaces or troughs between these detachments 

 giving rise to the East- Anglian vaUeys *, — valleys which, although 

 thus originating, were, as I shall show in the sequel, further modified 

 by glaciers from the land-ice of the Chalky Clay. 



The spaces thus excavated in and through the Contorted Drift 

 have been to a great extent occupied with the gravel c, so that the 

 beds of Stage II. protrude in bosses through it. 



The progress of this rise during the accumulation of the Chalky 

 Clay is shown by the position of that clay (d) relatively to the 

 gravel of greatest submergence (6'), and other formations of 

 Stage II., in the accompanying figures and Map If. 



Fig. YI. shows this along the southern edge of that clay, fig. YII. 

 along the eastern :|:, and fig. YIII. along the north-eastern — the 

 highest part of the gravel marked c in this last figure being, as before 

 explained, partially coeval with that marked 6 ^ in the other two 

 figures, as well as in figs. II., III., lY., and Y. The amount of 

 emergence which had taken place when the ice to which this Chalky 

 Clay was due decayed, I shall examine in the sequel ; but from the 

 clay spreading up against the flanks of the islands, shown in 

 figs. YI. and YIII., some way above the sea-level of the time, the 

 amount of this rise is not indicated by the upper limit of the Chalky 

 Clay in these figures. 



* See Harmer and myself in Quart. Journ. Geol. Soc. vol. xxxiii. p. 74. 



t The delineation of the Chalky Clay in this map is, with the exception 

 of Sheet 7, from my own work and that of Mr. P. W. Harmer in Norfolk ; 

 save that in the east of Sheet 46, south-west of 70, and south-east of 71, I have 

 been favoured with more accurate delineation from Geological-Survey sources, 

 through Mr. Whitaker. Sheet 7 is from the Survey map, and is the only 

 sheet of it that I have seen in which the Glacial beds are given. In the north- 

 west of Sheet 66 some of the clay is concealed, or its place is taken by the 

 gravel e' ; but as this gravel has resulted from the washing-out of the clay, as 

 described in Stage TV., and it cannot be seen how far the clay may have been 

 thus removed, and both are so mixed up in alternate patches that, on the very 

 small scale of the map, they would be difficult of separation, the whole is shown 

 as the clay. 



\ In this figure VII. the bending of the shading representing the London 

 Clay was intended to show the folding of the older strata within this hill ; but 

 from a section on the true scale furnished me by Mr. Dalton, of the Geological 

 Survey, under whose observation the late well-borings throiigh to this hill have 

 come, the fold is much greater than I have here shown it, and so much so as 

 to bring beds III. and lY. above the datum line in the centre of this figure. 

 It is, in fact, exactly that fold which, in the Phil. Mag. for 1864, I showed, 

 hypothetically, should occur at each successive concentric arc of the series of 

 which this hill formed a part. 



