PlIOCENE PEKIOD IN Eiq-GLAIfD. 489 



snow upon it during summer, and issues beneath that ice ; and the 

 sediment from this produced the first or lowest marl band. Winter 

 intervening, this ceased, and for the time the deposit of sand was 

 resumed, giving rise to the thin band of that material which divides 

 the two thin bands of marl from each other. When from the summer 

 meltings the stream of silt poured out again, the upper marl band 

 was laid down ; and before this again ceased the moraine itself came 

 upon the spot by a process of slide, the material being, from the 

 water present in it, in the mobile condition of mud. 



The commencement of the cutting-out process was (when I drew 

 it in 1864) visible at two points in the long section of the clay rest- 

 ing on c given by the North-Suffolk Cliff, in Sheet 67, at Hopton, 

 the clay being in these spots pressed down into the subjacent sand 

 and gravel c, which near the junction was in consequence disturbed 

 and squeezed outwards, and the hollow produced by the pressing 

 down was filled with the gravel e' resting on the clay. In these 

 instances the process went no further; but where the Waveney 

 valley cuts through the low tableland, of which this North-Suffolk 

 Cliff forms the section, the clay passing through the gravel c plunges 

 sharply into that valley down to and under the alluvium, cutting out 

 that gravel in the same way that is shown in the case of the Black- 

 water valley by fig. VII. 



Pig. XIY. represents the same thing, and is taken from the edge 

 of the Blyth valley at Bulchamp, the plunging clay lying like a wall 

 against the sand and gravel ; and it was this which, in the earlier 

 days of my investigation, misled me into the idea that the formation 

 was faulted. 



In fig. XI. the seam of d intercalated in c may so appear from 

 the section intersecting the point of the mud-bank as first laid down, 

 followed by a resumption of gravel accumulation before the bank 

 advanced again, or it may be due to the dropping of material dragged 

 from the adjacent mud-banks by floe-ice. 



In the north-east of Sheet 45 and south-east of 53, the junction 

 was preceded by the introduction into the gravel of a large number 

 of rounded boulders reaching to the size of a horse's head, just as in 

 Sheet 48 it was preceded by the introduction of rolled chalk. This 

 I found in a large section at Burcott Wood, near Towcester, in 

 Sheet 53. 



In the Proceedings of the Birmingham Natural-History Society 

 for 1870, a section at California, near Birmingham (in the south 

 centre of Sheet 62), is given with a detailed description by Messrs. 

 Crosskey and Woodward. This, as it seems to me to show in a 

 striking manner both the mode in which the Chalky Clay came upon 

 the sea-bottom, and the way in which the allowance must be made 

 between sea-bottom and sea-top in tracing the level of the sea at the 

 close of that formation, as I do in Stage Y., by the height of the 

 gravel over that clay in the parts where it then entered the sea, I 

 have copied for illustration here as fig. XYII., altering it only to 

 the extent of applying to the several beds the indicative letters 

 which correspond to those used in the other figures of this memoir, 



Q.J.G.S. No. 144, ^1 



