190 Correspondence. 



On examining the Crag pit of Thorpe more closely, I found the 

 pebbly sands of the Bure valley to cap the pit section, resting upon 

 the attenuated Chillesford clay. Mr. Harmer had detected a bed of 

 blue clay, about twelve feet thick, interstratified with sand bands, 

 over a considerable area on the south-east of Norwich, which was 

 quite distinct from the before-mentioned green clay. This I at 

 once recognized as the Chillesford clay, and found it to be present in 

 the Crag pits of Brundall, Bramerton, and Thorpe, attenuating in 

 the latter to half its usual thickness; the Chillesford shell-bed oc- 

 curring in all three, in its usual place in the sands beneath the clay. 

 The exposure of (so-called) Crag at Toftmonks, in the Waveney 

 valley, made known by Mr. Eose, I recognized also as the Chilles- 

 ford clay and shell -bed ; and was thus enabled, by an almost con- 

 tinuous line of sections, to trace these clays from Norwich, where 

 they pass under the Bure Valley beds and green clay, to Easton 

 cliff, from which they are admitted to extend to Chillesford. 



On analysing with my father the fauna (as far as known), we 

 found the sequence of the four formations to be in the following 

 ascending order, viz : — 1, Fluvio marine Crag ; 2. Chillesford bed ; 

 3. Bure valley beds; 4. Weybourne sand (or so-called Norwich 

 Crag of the coast) ; which precisely agreed with their position, de- 

 duced by me from the sections as above explained. I was then 

 satisfied that I had been misled by the apparent transition from the 

 Chillesford clay to the Middle Drift, which the sections around 

 Orford, Sudboum, and Chillesford seemed to indicate ; and I took 

 the opportunity of a note to the structural diagram of the beds from 

 the Eed Crag upwards, which I gave in my father's paper on the 

 Eed Crag (Quarterly Joixrnal of the Geological Society, Vol. xxii., 

 page 552), to correct this error; and I had hoped in a manner 

 sufficiently intelligible. 



The green clay, before mentioned, changes southwards from 

 Norwich, first into a red loam — in which form it comes up beneath 

 the Middle and Upper Drift, at the base of the Coast Section, 

 between Yarmouth and Lowestoft, and at Pakefield Cliff ; and then 

 into red sand, in which form it is present over the pebbly Bure 

 valley sands on the top of the Covehithe and Easton Cliffs, and 

 comes up beneath the Middle Drift in the lower part of Dunwich 

 Cliffs. About this part also the Bure Valley beds lose their pebbles ; 

 and thus all the beds between the Chillesford clay and the Upper 

 Drift, becoming, as they approach Orford, Sudboum, and Chillesford, 

 simple sand, the illusory appearance of this part of the area is pro- 

 duced. 



I take the opportunity of demurring to the altitude of any glacial, 

 or post-glacial, bed, being regarded as a test of its age, except 

 where two beds occur in close contiguity to form a terrace ; and then 

 no further than as a test inter se. I hardly think that Mr. Maw is 

 aware that the clay, of which he speaks as occupying heights from 

 150ft. to 230ft. above the sea, descends from High Suffolk and 

 Norfolk (underlaid by the Middle Drift) gradually to the sea level at 

 Scratby Cliff; and to within 30ft. of it at Corton and Pakefield 



