Correspondence. 189 



[The Editor has had the pleasure, on three occasions, to see and 

 examine Mr. Pengelly's interesting rock-specimens, exhibiting Mol- 

 luscan borings, and he has no hesitation va referring them to Pholas, 

 as they agree perfectly with specimens in the late Dr. Woodward's 

 cabinet, which still contain the valves of Pholas within the cavity.] 



[We are requested by Mr. Mackintosh to correct his letter in our 

 last No. as follows : — Page 137, line 16, for "planes," read plains — 

 line 30 for " These," read Those ; page 138, line 1 (in notes) for 

 " these," read those — line 4 (in notes) delete " which " — line 16 (in 

 notes) for " dualogical " reasoning, read analogical reasoning.] 



AGE AND POSITION OF THE DEIFT DEPOSITS OF THE EASTERN 



COUNTIES. 

 To the Editor of the Geological Magazine. 



Sir, — You will, perhaps, allow me to explain, and correct, an 

 opinion which Mr. Maw, in his paper in the last number of the 

 Magazine, has attributed to me. 



He quotes (page 99) my expression that the Chillesford beds are 

 evidently part of the Middle Drift : but he seems to have overlooked 

 a qualification of that opinion which I subsequently made. When 

 the remarks which Mr. Maw quotes were written, I had traced the 

 Till and Contorted Drifts of the Cromer coast (a and b of Mr. Maw's 

 fig. 1), from the Weybourne extremity of the coast section into a 

 marl, which passed inland under the Middle Drift (or bed D of the 

 figure), until I found it thin out against the Chalk, before the Crag 

 district was reached. Hence, as the Middle Drift was a capping bed 

 common to these beds, the Crag, and the Chillesford clay, alike, I 

 was induced from the appearance of the latter at Chillesford, Sud- 

 bourn, and Orford, to regard them as belonging to the lower part of 

 the Middle Drift formation. Subsequently to this, however, I suc- 

 ceeded in tracing the beds of the Cromer coast from the other, or 

 Hasboro', extremity of the coast section (which I had previously 

 only traced under the Middle Drift sands as far as North Walsham) 

 completely over the Chillesford clays, and the Fluvio-marine Crag 

 of Norwich. 



In doing so, I availed myself of the labours of Mr. Harmer, of 

 Norwich, who systematically worked out and mapped a considerable 

 area on the east and north of that city. This gentleman foimd that 

 the Green Clay worked for bricks, into which the Cromer beds pass 

 from Hasboro', by North Walsham, to the Bure Valley, had an ex- 

 tensive spread beneath the Middle Drift on the north of Norwich ; 

 and with it passed under the Upper Drift, at Trowse and Arming- 

 hall, on the south of the city. This green clay in the Bure Valley 

 is underlaid by a sand containing pebble beds, which, at Coltishall 

 and Wroxham, yields a small proportion of the shells of the Fluvio- 

 marine and Eed Crags, and of the Chillesford bed, Mr. Harmer 

 and myself found this green clay to pass over the Crag, a pit of it 

 occurring on the hill above the Thorpe pit, and close to it. 



