300 Mr. S. V. Wood on the Red Crag 



the high lands of the north of England would exempt them from 

 any part that glaciers may have played in the distribution of the 

 great boulders of that part of England. 



Notwithstanding the confusion that has existed as to the rela- 

 tionship to the Drift borne by the freshwater formations of Grays, 

 Ilford, Clacton, Stutton, Copford, Lexden, Hoxne,&c., I take it to 

 be now well understood that these and similar formations in other 

 counties are altogether posterior to the Drift period, having been 

 deposited in the valleys that resulted from the upheaval of the bed 

 of the upper-Drift sea, and from the denudation that accompa- 

 nied such upheaval. Being limited for space, I have not referred 

 to these beds, but confined myself to marking into the map 

 of the Red Crag district the only deposit of this nature (that of 

 Stutton and Wrabness) occurring within it. It will be seen that 

 the Stutton and Wrabness beds rest on the London Clay, which 

 previously to their deposition had been laid bare by the denu- 

 dation of both Drifts, and which denudation accompanied those 

 symmetrical movements that elevated the upper-Drift sea-bed, and 

 gave rise to the inequalities of surface over the East of England 

 which form the subject of my paper on the valley-system before 

 alluded to. The other correlated freshwater deposits named 

 above are identical with that of Stutton in their position rela- 

 tively to the Drift, although they vary in the bed they rest upon, 

 according as the denudation has in a greater or less degree 

 eroded the valley previous to their deposit ; but, within the limit 

 of the period elapsed since the upheaval of the Drift sea-bed, 

 these deposits may to a small extent vary in age among them- 

 selves. The greater contiguity of the Thames valley to the 

 centres of upheaval producing the valley-system, but more par- 

 ticularly its greater contiguity to the great rectilinear upheavals 

 of the Weald and South of England which succeeded the gene- 

 ral upheaval producing the valley-system, has, as I conceive, 

 caused in that vaUey greater changes of level among its deposits 

 than is the case with the beds accumulated in the valleys of the 

 rivers of northern Essex. The precise correlation in age of the 

 valley-deposits of the respective areas is therefore, I think, to 

 be satisfactorily arrived at rather by close palseontological analy- 

 sis than by comparisons of level and physical structure. 



Appendix. 

 Sections of Red Crag. 



Alderton. On the Ramsholt road, three-quarters of a mile from Alder- 

 ton. — Fifth stage, laminated with red sands, and false-bedded. 

 No line of erosion visible. Traces of a beach stage at bottom. 

 Nodule-band occurs. 



Bawdsey, Sea-cliff. — Fifth stage. Fourth and two other beach stages. 



