552 Fisher — Denudations of Norfolk. 



Here we have the coarser materials from which the finer particles have been 

 carried off to form loam elsewhere (an ancient manufacture of " whiting " on a 

 magnificent scale). 



The occurrence of masses of glacial materials in isolated or anomalous positions, 

 as for instance at Gallows Hill, on the side of the Chalk valley above Burnham, 

 and in a pit just beyond Harford Bridges, on the Ipswich road from Norwich, 

 may, I think, be referred to this kind of action and to this period, and I am glad 

 to find that the conclusion I came to upon the ground as to the age of the recon- 

 structed Chalk agrees with Mr. Trimmer's, who places it in his Upper Drift, ^ that 

 is the Middle Drift of Mr Wood. The denudation to which the Chalk must have 

 been subjected during the period of the Middle Drift, upon which we are now enter- 

 ing, must have been enormous. Bear in mind how small a portion of the bulk of the 

 Chalk is formed of flints, and then consider the immense beds of sand and gravel, 

 coarse and fine, derived from chalk flints, out of which by far the larger portion of 

 the thick and extensive outspread of the Middle Drift is formed. In the drift 

 gravels of many parts of Norfolk, as I am informed by Mr. Gunn, great numbers 

 of flints, containing a peculiar sponge, occur. I have seen them myself in abun- 

 dance in the coarse bouldered gravel overlying the Lower Drift at Wayford Bridge. 

 Now the bed of Chalk containing these flints is nowhere to be found except on the 

 shore, and in the remarkable bluff already alluded to near Trimmingham. Every- 

 where else that bed of Chalk has been denuded, and much of it, as these flints show, 

 during the period of the Middle Drift. 



It is in the lower part of this middle member of the Glacial Drift, where these 

 great bouldered flints principally occur. They are mixed with coarse gravel, and 

 may be seen in the pit at Wayford Bridge, and many other places. They cap the 

 lofty cliffs at Beeston and Beacon hill, and cover the summits of the picturesque 

 ranges round Cromer. Mr. Wood's opinion is that this Drift was a littoral deposit, 

 formed during an amelioration of climate.^ Mr. Trimmer, however, remarks that 

 an examination of the soundings recorded in Polar voyages, particularly those of 

 Sir Edward Parry, proves that in frozen seas, mud, which under ordinary conditions 

 is regarded as a deep water deposit, is characteristic of the vicinity of land, where 

 sand and shingle would prevail in other seas.^ Though not stated so, the converse 

 appears intended to be asserted. 



I think we may say that very little beyond its geographical boundary is known 

 about this stratum. I lived upon it in Essex for several years, but, except collect- 

 ing a variety of pebbles from the old rocks, and one of them ice-worn, I could 

 learn little definite about it. I once found a few fragments of a Bivalve, probably 

 of a Tellina, from a sand pit in the valley at Hoxne, in Suffolk, which from its 

 position seems to belong to the Middle Drift. At a pit at Milend, near Norwich, 

 called Firgrove pit, a sand occurs, which appears to belong to this deposit, and 

 contains foraminiferse, derived, as Mr. Taylor tells me, from the Chalk and the 

 Boulder-clay. The former appear to be of the same species as those found in the 

 railway cutting near Wells. We owe almost all the definite knowledge we possess 

 about the Middle Drift to Mr. S. V. Wood, jun. He seems to be of opinion that the 

 sea, which deposited it, did not cover the highest lands, but we certainly find its 

 lowest beds in Norfolk, forming the crest of some of the highest hills in the north- 

 ern part of the county, and I think it is exceedingly probable that it overspread the 

 whole Chalk area.* 



There are patches of Boulder-clay, as for instance at Firgrove pit, and other 

 places around Norwich, which ai-e believed to belong to the Upper Drift. If so 

 the Middle Drift must have been greatly reduced in thickness by denudation before 

 they were deposited, or else it must have been originally much thinner hereabouts 

 than where normally developed. 



The Upper Boulder-clay or Upper Drift was first distinguished from the Lower 

 by Mr. Searles Wood, jun.* It is that stratum which, on account of its thickness 

 and great superficial extent, deserves the name of The Boulder-clay. The part of 

 Norfolk now covered by it is, however, comparatively small, though in Suffolk it has 



^ Geol. of Norfolk Jour, of Agr. Society, vol. vii., p. 463. 

 2 Remarks in explanation of Map of Upper Tertiaries, p. 12. 

 s Journal of Geological Society, vol. vii., p. 21. 



♦ Sands were seen about Docking on high Chalk land, which appeared to be Glacial. 



* Remarks in Explanation of the Map of the Upper Tertiaries, pp. 12, 22. 



