74 



become estuarine at Erith I think it must have been very 

 nearly so. At all events the waters were raised so high 

 that the gravels of the Darenth accumulated in its bed. 

 and sands and clays completely choked it (viz., the Erith 

 and Crayford Brickearths), rising as high as to retouch 

 the gravel on the higher terrace of Dartford Heath, &c. 

 On the subsidence of this high water level which was 

 accompanied by aggravated glacial conditions, and strong 

 floods, the old bed by North End being blocked, the 

 stream of the Darenth cut through and washed away the 

 obstructing mass of chalk and established the present 

 stream line at a deeper level than the old one by Erith. 



The Thames after the last rise, excavated its bed at 

 Erith for another 50ft., laying freshwater gravel which is 

 there now. But after that depth had been reached, subsi- 

 dence set in, the bed has become choked with sand, con- 

 taining estuarine shells and tidal clay in layers, with peat, 

 and forest growth, alternating. The depression continues 

 still, as is shown by the deposit of Tidal clay over 

 marginal banks of gravel sprinkled with relics of Roman 

 occupation and more recent remains ; as well as by the 

 existence, many feet below the surface of the marsh, of the 

 foundations of dwellings of Roman and mediaeval con- 

 struction.* 



Flint implements are found at different levels over the 

 whole district in positions which shew a great difference 

 in their relative age and in the conditions under which 

 they were deposited. They are found, some worn by 

 longer or shorter travel with others apparently unworn, in 

 the higher level gravels of Plaxtol, Bewley, and Chart 

 Farm (Ightham) ; gravels which were deposited by a river, 

 not the JMedway nor the present Darenth, but by a former 

 stream whose bed now lies on the line of the water-parting 

 of both. Implements are also found at levels higher than 



* See Journal of the Archaeological Institute, \'ol. xlii. p. 269, 

 "Early Sites on the Thames Estuary." by F. C. J. Spurrell. 



