592 MESSRS. JUKES-BROWNE AND W. HILL ON THE LOWER PART 



their appearance below, and the marly beds thin out, till at and 

 beyond Grimston the whole division consists of hard chalk. 



3. That for a certain distance its basement-bed is a glanconitic 

 marl, but that this thins out beyond Marham, and the overlying 

 bed of hard white limestone then forms its basal layer. 



4. That microscopical examination shows that the proportion of 

 Foraminifera and recognizable shell-fragments increases as the beds 

 are followed northward, and that the hard beds of north-west 

 Norfolk may be regarded as the condensed equivalent of the true 

 Chalk-marl, differing from it by the greatly reduced amount of 

 inorganic matter and of glauconite grains. 



Red Chalk. — We are now in a position to indicate the bearing 

 of our work on the debated question of the exact age of the Red 

 Chalk. In the absence of anything like ordinary Gault, Upper 

 Greensand, or Chalk-marl at Hunstanton, the remarkable stratum 

 which there lies at the base of the Chalk has been referred by 

 different observers to each of the formations which appeared to be 

 missing — to the Gault by most of the earlier writers and by Mr. 

 Wiltshire, to the Upper Greensand by Prof. Seeley (on the strength 

 of its fossils being similar to those of the Cambridge Greensand), 

 and, lastly, to the Chalk-marl by Mr. Whitaker. Everyone, however, 

 has discussed the question principally from a local point of view, 

 founding their arguments mainly upon a consideration of the rock 

 and its fossils as seen at Hunstanton. It is true that Mr. C. B. 

 Rose and Mr. Wiltshire both obtained some items of stratigraphical 

 evidence, but they were rather meagre, while the value of Mr. 

 Whitaker's remarks is diminished by his having then mistaken the 

 Upper Gault of Norfolk for Chalk-marl. 



It was evident, therefore, that the problem could only be solved 

 by following up the component beds of the Gault and Chalk-marl 

 from an area in which they were more normally developed. Such 

 stratigraphical work, however, was by no means easy ; for these 

 strata form a low-lying tract of country, where natural or artificial 

 exposures are few, and where they are often concealed by spreads of 

 Boulder-clay and gravel. We think, however, that the borings we 

 have made, and the facts we have observed, are sufficient to deter- 

 mine the stratigraphical relations of the beds we are discussing. 



As already stated, we have ascertained that in Norfolk there is a 

 complete but rapid or sudden transition from Upper Gault to Chalk- 

 marl, without the intervention of any quartzose or glauconitic 

 sands ; but we would point out that these are not exceptional relations, 

 and that the Stoke and Shouldham sections may almost be matched 

 near Ivinghoe in Buckinghamshire and Totternhoe in Bedfordshire. 

 At both these places there is an entire absence of anything which 

 can truly be called Upper Greensand, and there is a complete passage 

 from marly Gault into Chalk-marl, the passage-bed being a dark- 

 grey marl with many spangles of mica and small grains of glauconite. 

 The explanation of this passage is that the sands and rock-beds of 

 the so-called Upper Greensand have been gradually replaced by the 

 marls of the Upper Gault, while the green glauconitic marls seem 



