XVIII. On the Geology of some parts of Suffolk, particularly of the Valley of the 

 Gipping. By J. B. Phear, Esq. M.A. F.G.S. Fellow and Assistant Tutor of 

 Clare Hall, Cambridge. 



[Read Feb. 27, 1854] 



The general features of the county of Suffolk point it out as a district where some portion, 

 at least, of the Drift phenomena may be advantageously studied. It is bounded on the West 

 and North-west by chalk uplands, on the South and East by the sea, and the area thus 

 enclosed is occupied by a mass of drift-clay which several main valleys with their ramifications 

 cut into undulations of some depth and abruptness. 



The county is singularly divided from Norfolk by a marked depression through which the 

 Waveney flows eastwards and the Ouse westwards ; the courses of all the streams, with the 

 exception of the Lark, which joins the Ouse and finally discharges itself at Lynn, run towards 

 the South-east coast and are approximately normal to it : of these the most considerable is 

 the Orwell or Gipping, and it is worthy of remark that its valley is parallel to, and almost 

 continuous with, all the important part of the valley of the Lark on the other side of the 

 county : both seem to be perpendicular to the general strike of the chalk in this locality. 

 The few miles of high ground which intervenes between them consists of chalk very partially 

 covered with drift of any kind, and scarcely anywhere with any amount of drift-clay. It is 

 impossible not to be struck, at a first glance, with these transverse sections of the chalk-range. 



On pursuing the streams towards the coast, the central mass of clay is found almost 

 entirely to cease upon reaching a line (hereafter to be more particularly defined), whose maxi- 

 mum distance from the sea may be roughly stated at twelve miles : London clay here comes to 

 the urf' e, covered in many places (and almost universally upon nearing the coast-line) by 

 cra^ and other marine and freshwater deposits, and still more superficially by a layer of unfos- 

 siliferous sand, which may probably be associated with the drift. 



The name drift is generally made to include a great variety of materials, such as sand, 

 gravel, rough clay, of every degree of coarseness, but all sharing the common characteristic 

 of an almost entire absence of stratification or apparent law in their arrangement. The clay 

 is very far from being homogeneous, but is generally of a colour varying from blue to grey ; 

 sometimes however it is brown, and at others the excessive prevalence in it of chalk nodules 

 gives it a yellowish white hue : perhaps these variations of colour point to real distinctions in 

 the conditions of deposit; and it may be mentioned as an approximate law that the deeper blues 

 seem to be found at the greater distances from the chalk, and that the sterile yellows form some 

 of the high grounds. It is very full of all kinds of rock, from lias to chalk inclusive, and is 

 especially rich in specimens of septaria belonging to the Oxford and Kimmeridge clays and the 

 Vol. IX. Part IV. 56 



