A HISTORY OF BUCKINGHAMSHIRE 



above the level of the highest flood waters in the river. The gravels 

 hold a considerable amount of water, which rises according to the rain- 

 fall, or in other words, according to the amount of water in the river, 

 and thus basements of houses may be rendered damp. 



Looking generally to the relation between the geological structure 

 and the early settlements, we find in Buckinghamshire as in other 

 counties that the question of water supply from river, spring, or well 

 was the natural guide in the fixing of sites. In the deeper Chalk 

 valleys where springs break out and streams flow, along the base of 

 the Chalk escarpment and of the Upper Greensand, on outliers of 

 Lower Greensand and Portland Beds or along their margin, and on 

 the Great Oolite Series, there we find the principal villages and towns. 

 On the clay areas the settlements were fewer and less important, for 

 only where patches of gravelly Drift occur could local supplies of water 

 be readily obtained. 



