280 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Jan. 23, 



With regard to the condition of the sea immediately anterior to the 

 period of the deposition of the basement bed of the London clay, it is 

 probable that the whole, or nearly so, of the south-east of England 

 was occupied by the Eocene sea, studded with a few islands. An 

 important one may have existed at some point between Woolmch 

 and Newhaven (unconnected however with the elevation of the 

 Wealden as it has since taken place) . On the shores of these islands 

 small rivers accumulated fluviatile and estuary deposits, such as 

 those of Woolwich, New Cross, Upnor, and Newhaven, whilst further 

 eastward marine deposits were accumulating in the open sea stretch- 

 ing to, and probably beyond, the now Isle of Thanet. 



In this state of things a movement of depression probably took 

 place over this district in a direction W.S.W. toE.N.E. from Hamp- 

 shire to Suifolk, whilst a corresponding and coseval elevation took 

 place perhaps on a parallel line further south, and passing, I am 

 rather inclined to believe, south of the Isle of Wight towards the 

 north of France, and not touching upon the area now occupied by 

 England. From off this raised sea-bed to the south, a wave of trans- 

 lation (if the term may be applied to deposits of this period), of mo- 

 derate power and having a N.N.W. flow, would be thrown, spreading 

 over the bottom of the sea, debris derived chiefly from the older 

 eocene sands and pebble beds forming the bed of the sea over which 

 this wave moved. This wave would decrease in force as it receded 

 from the axis of elevation, whence the diminished erosion of the 

 surface, and the generally smaller size of the pebbles, in Essex and 

 Suffolk. The spread of this debris would afterwards be further mo- 

 dified and extended by currents. At the same time, the sea, then 

 of moderate and tolerably uniform depth, was extended over a larger 

 area than it before occupied. The ancient river-courses were altered, 

 their deposits ceased wholly or partially, and no new rivers yet came 

 into full operation, for the fauna lived and flourished on a sea bed 

 which evidently received but little addition of sediment during this 

 period. Over the eastern part of Kent, however, the actions of cur- 

 rents and perhaps of small rivers still led to the accumulation of 

 deposits of fine sands, increasing in thickness from two to three feet 

 near London to twenty feet at Heme Bay. 



Westward of London in no case does the basement bed of the London 

 clay present a thickness of more than five feet, and in many places it 

 does not exceed one foot. Where the passage from this stratum to 

 the mass of the overlying London clay is gradual (see Sections 1, 5, 

 & 12), fossils usually abound, especially near the line of junction ; while 

 if the argillaceous beds repose at once on a compact and separate 

 layer of pebbles, few or no fossils are found (see Sections 3, 7, 8, 17). 



This profusion in some localities of organic remains, and their 

 dispersion over so wide an area, render it also probable that, after 

 the first spread of the debris of pebbles and sand, a considerable in- 

 terval of time elapsed before the argillaceous beds of the London clay 

 began to accumulate, a process which however afterwards set in gra- 

 dually and without any mark of further disturbance, the necessary 

 physical changes having taken place at the period of its basement bed. 

 At the same time the occasional presence in this bed of the remains 



