.529 



In addition to these facts, Mr, Clarke says, that the estuaries of the 

 Aide, the Deben, the Orwell, and the Stour, having an average length 

 of 1 1 or 12 miles, meet the fresh water at nearly the same distance 

 from the sea, and at the boundary line of the great continuous bed of 

 diluvium, which covers so extensive an area in that part of England ; 

 only detaclied patches of greater or less extent, being found to the east 

 of the line. 



The Gkoi.ogical Structure. — The formations of which Suffolk 

 consists, are chalk, the plastic and London clays, crag, diluvium or an- 

 cient superficial detritus, and recent lacustrine deposits ; the first occu- 

 pying the N.W. portion of the county, the second, third, and fourth the 

 south-eastern,and the fifth or diluvium, the intermediate part, res tingon 

 all the preceding deposits ; while the sixth or lacustrine accumulations 

 are of very local occurrence. 



Chalk. — This formation in the S.E. of Suffolk, is principally exposed 

 in the banks of the estuaries and rivers, and contains the usual plates 

 and nodnles of flints, as well as the fossils characteristic of the upper 

 chalk. In making a well at Harwich, at the depth of 93 feet, and 

 between the white and grey chalk, a stratum 10 feet thick of sandy, 

 gritty chalk was penetrated. The beds are in general nearly horizon- 

 tal, declining gently to the south-east, but they sometimes dip at 

 considerable angles, and the surface appears to have been violently 

 dislocated and worn into deep guUeys, locally called sand-galls. At 

 Harwich in making two wells only 70 yards apart, the chalk was 

 reached in the northern at the depth of 88 feet, but in the southern at 

 64 feet. Where the formation has been denuded by the rivers, the 

 tertiary beds frequently rest upon it, but where it rises into an eleva- 

 tion above the river levels, it is covered altOii,ether by diluvium. 



Plastic clay. — There is some difficulty in separating this deposit 

 from the diluvium of Suffolk. At certain points, however, it displays 

 the samebeds of mottled clay and sands with pebbles, which characterize 

 it in other parts of the kingdom ; and it is occasionally exposed be- 

 tween the London clay and chalk. From its local occurrence Mr. 

 Clarke is of opinion, that it has been subjected to denudating agents, 

 and that it has partaken, in part at least, of the dislocations which have 

 affected the chalk. 



London clay. — This formation presents, in Suffolk, the usual cha- 

 racters. At Walton on the Naze and Bawdsey, considerable quanti- 

 ties of pyritous vegetable remains are washed up from a bed below the 

 level of the sea; and are said to rival in variety and abundance the 

 Sheppy fossils. The furthest western point at which the formation is 

 visible, is Layham near Hadleigh, the country beyond being covered 

 by diluvial clay. It constitutes, however, the substratum of all the 

 estuaries which intersect the S.E. of Suffolk, and the coast section 

 from Orford Ness to Walton Naze, being everywhere capped by crag. 

 This section is constantly varying in its features, but presented when 

 theautlior examined it, in 1827, the appearance of beds once horizontal, 

 having been upheaved in some places and depressed in others ; but 

 to what extent these disturbances may have been produced by elevatory 

 movements, the action of the sea, or the undermining of land springs, 

 he could not satisfactorily determine. The supply of water obtained 



