360 Rev. W. B. Clarke on the Geological Structure 



inclinations of the chalk ; and that the valleys of Norfolk are valleys of eleva- 

 tion due to the elevation and fracture of the chalk ; and in these statements I 

 fully concur. 



In addition to the preceding- facts it may be added, that the estuaries of the 

 Aide, the Deben, the Orwell, and the Stour, meet the fresh water at nearly the 

 same distance, 11 or 12 miles, from the sea, and at the boundary line of the 

 great continuous bed of diluviun>, which covers so extensive an area in that 

 part of England, patches only, of greater or less extent, being found to the 

 east of the line. 



2. The Geological Structure. 



The formations of which Suffolk consists are, 1, chalk ; 2 and 3, the pla- 

 stic and London clays ; 4, crag ; 5, diluvium, or ancient superficial detritus ; 

 and 6, recent lacustrine deposits ; the first occupying the N.W. portion of 

 the county ; the second, third and fourth, the S.E. ; and the fifth, or diluvium, 

 the intermediate part, resting on all the preceding deposits ; while the sixth, 

 or lacustrine accumulations, are of very local occurrence. 



1. Chalk. — In the S.E. of Suffolk this formation contains the usual plates 

 and nodules of flints, and the fossils characteristic of the upper chalk. In 

 making a well at Harwich, the workmen penetrated, at the depth of 94 feet, 

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

 gritty chalk. The beds are in general nearly horizontal ; but they are some- 

 times inclined at considerable angles, and the surface appears to have been 

 violently dislocated, and worn into deep gullies, called, locally, 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. The 

 variation in the dip of the beds is considerable. At Shelley and Greeting 

 they rise to the N.E. ; at Monk's Eleigh, scarcely 9 miles distant, to the S.W., 

 at an angle of 15° ; at Offton the rise is also to the S.W. ; but at Hartest to 

 the N., and at Blakenham to the S.* 



The general slope of the chalk is from N.W. to the sea. At Sudbury, 

 where it cuts the Stour level, it is about 70 feet above the sea ; and at East 

 Bergholt about 16 feet; but at Harwich, from 64 to 88 feet below the sea- 

 level. Again, at Wickham Market the chalk was reached at the depth of 

 160 feet; and at Woodbridge, six miles distant, at 250 feet from the surface. 



Where the formation has been denuded by the rivers, the tertiary beds fre- 

 quently rest upon it; but where it rises into an elevation above the river- 

 levels, it is covered altogether by diluvium. 



* For references to detailed sections of the chnlk, see numerical index, j). 369. 



