88 



As the land continued to rise and increase in extent, rain 

 would fall upon its surface, perhaps in greater quantity than at 

 present ; streams and rivers would come into existence, still 

 further arranging both the Boulder Clay and the coast-gravels 

 previously formed ; and these rivers would have a general 

 tendency to flow from the dominant ridge towards the N.W. 

 and S.E., the northerly tendency being increased in Cambridge- 

 shire by the slope of the country towards the estuary of the 

 Wash, which was in existence before the incidence of the 

 Upper Glacial Clay, 



Taking the above as an outline of what Avould probably 

 happen during such an emergence of East Anglia as was 

 initially supposed, it is satisfactory to note that all the deposits 

 described in this Essay are fully accounted for by such a series 

 of events, and that their relations to one another are perfectly 

 explicable on this hypothesis. 



The " Hill gravels " and their probable equivalents, the 

 " Plateaux" or " Flood gravels," seem to have been accumulated 

 rapidly, and like the Middle Glacial sand and gravels they are 

 apparently marine ; yet so closely are they connected Avith a 

 second set of gravels which are clearly of fluviatile origin, that 

 no long period of time can have intervened between the forma- 

 tion of the two series ; the conditions which caused the pro- 

 duction of the former seem also to have led to the formation of 

 the latter, and from this time to the present there is no reason 

 for supposing that East Anglia has been subjected to any other 

 influences than those of rain and rivers. 



Tui'ning now to a consideration of the changes that have 

 taken place since the emergence of the country from the glacial 

 sea, the evidence afforded by the series of ancient river gravels 

 leads to some interesting results. 



It is indeed a significant fact that in these higher districts 

 the gravels have a recognisable relation to the existing valleys, 

 while when they emerge upon the plain country all such con- 

 nection is lost, and the direction which they take across the 

 country is quite irrespective of the present river system. 



We may at once conclude that the outline of the hill 

 country has not changed so much as that of the plain, and that 

 its present valleys are but the more deeply excavated tormina- 



