452 Sir E. H. Rou-orth— 



on the north. In the west its limits have not been quite defined, 

 but it occurs abundantly in Leicestershire and Kutland, in Bedford- 

 shire and Buckinghamshire, in Nottinghamshire, and parts of Stafford- 

 shire and Warwickshire ; on all sides it is limited, however, by 

 other beds, and forms a great concentric ribbon or ring round the 

 Fen country. 



The lesson I wish to deduce from these facts is, that the chalky 

 nature of this clay in certain places is no criterion of a separate 

 origin and a separate history for the deposit. It means no more 

 than that the same clay, where it lies on or near chalk, is chalky ; 

 where it lies on or near Oolitic beds, is largely Oolitic ; and where it 

 lies on or near Liassic beds, is Liassic. Where, again, it is remote from 

 chalk, chalk debris is necessarily not present in it, and yet the clays 

 may be, and probably are, of the same age, produced by the same 

 forces, and differentiated from each other only as the sandy deposits 

 of one part of a bay are differentiated from the muddy deposits of 

 another part of it ; — the fact is that the Chalky Clay, which, in 

 the eyes of so many geologists, forms a deposit which is treated 

 as sui generis, and as marking a particular horizon, is nothing of 

 the kind, but, as I believe, is merely a local form of other clays 

 occurring in Eastern England, which do not contain chalk debris, 

 but which resemble it in other respects, and which are, so far as we 

 know, interlocked with it or mark the same horizon. This very 

 fact, however, involves an issue of importance ; for it may well be 

 that where the chalk debris was not available for incorporation in 

 the clay, the clay itself may be of precisely the same age, and be 

 otherwise continuous with the Chalky Clay ; and that instead of 

 there being several superficial clays in Eastern England, whose 

 various names, such as Stony Clay, or Hessle Clay, or Purple 

 Clay, etc., suggest a varying origin, there may be only one such 

 clay, marked in different areas by necessarily different characters, 

 pointing, not to a different date, but to different ingredients, and 

 perhaps a different provenance. 



Two Boulder -clays have been described from Norfolk — the 

 Upper or Chalky Boulder-clay and the stony loam or- Lower 

 Boulder-clay. The difficulty of separating the two may be judged 

 from the following sentence of Mr. H. B. Woodward. He says : 

 — " So little brick-earth is met with that for a long time I could 

 not settle in my mind whether or not the Chalky Boulder-clay 

 was distinct from the stony loam. The absence or rarity of 

 this formation where the Lower Glacial brick-earth was well 

 developed seemed to favour the notion. The apparent passage 

 of stony loam into chalky loam at the brickyard in Long John's 

 Koad, also in the railway -cuttings north-west of Hapton ; the 

 difficulty in the parishes of Postwick, Brundall, and Plumstead of 

 drawing a line between the Chalky Boulder-clay and the stony loam, 

 where the two . seem from their physical relations to merge one 

 into the other, tended to support the supposition that they were 

 but one formation." Mr. Woodward quotes the pits at Upton Ham- 

 lington and South Walsham as throwing some light on the subject 





