82 Mr. Charlesworth on the Crag-formation 



same district. These works, however, refer particularly to 

 the crag of Norfolk, which it will be seen does not present 

 nearly so extensive a series of fossils, or perhaps such inter- 

 esting geological features, as the same formation in the ad- 

 joining county. I must also mention the observations made 

 by Mr. Lyell during a survey of the Norfolk and Suffolk 

 coasts in the summer of 1831, and which are so ably de- 

 tailed in his Principles of Geology. 



The latest published account of the crag is in Professor Phil- 

 lips's Guide to Geology*, which I quote as illustrating the 

 notions commonly entertained respecting the character of this 

 formation. 



" Crag-formation. Mineral character, — It resembles 

 almost exactly a shingle or pebble beach with layers of sand 

 and shells, being composed of pebbles of various sorts, rolled 

 and worn fish-teeth and bones ; a few bones of quadrupeds, 

 also worn ; many shells, sometimes worn, sometimes not ; parts 

 of Crustacea, Polypifers, &c. The whole has an ochraceous 

 aspect from the admixture of oxide of iron. In one situation 

 a coralline limestone of the same age occurs, and includes 

 several of the same shells." 



This extract gives a very good idea of the appearances often 

 presented by the crag, and particularly by those portions 

 which have hitherto fallen under the inspection of geologists: 

 but there is a very important part of the formation to which 

 the description is by no means applicable, whether we regard 

 its general mineralogical characters, or the apparent circum- 

 stances under which its organic remains have been deposited. 



The crag of Suffolk rests on a substratum of clay, which, 

 though often differing in character from the blue clay of Lon- 

 don and Hampshire, probably belongs to that formation, as 

 numerous teeth of fish and occasionally large Nautili are 

 found in itf. 



The most favourable situation for viewing the crag as it 

 usually occurs is along the south-eastern coast of Essex and 

 Suffolk, where its bright sands, mixed with prodigious quan- 

 tities of worn and broken testaceous remains, are seen topping 

 the cliff; the beds varying in thickness from five to twenty 

 feet. Here the crag rests unconformably upon the London 

 clay, without any material alteration in its character or ap- 

 pearance. The continuity of the stratum is interrupted by 



* A Guide to Geology, by John Phillips, F.R.S. &c. Second edition, 

 1835. p. 104. 



T A splendid Nautilus, found beneath the crag, adorns the chimney- 

 piece ofa cottager by the fort at Walton. I have also seen several at 

 Walton-on-the-Naze in Essex. 



