Water Supply. 281 



water, once flowing' to the surface, does not now attain that level 

 by a few feet; their depth is said to be from 130 to 140 feet. 

 The water from wells sunk through the gault is slightly ferruginous, 

 as mig'ht be expected from the nature of the gi-eensand, whence 

 it rises. At Grenelle, where there are the same geological con- 

 ditions, the water is often used for hospital purposes, and it is a 

 practice to place glass vessels in the flowing water, where they 

 acquire a yellow tint. As the water in the lower greensand has 

 no defined outfall, and as the depth of the gault clay varies, no 

 rule can be laid down. The greensand will g'enerally be reached 

 under 150 feet, the water will seldom rise to the surface, therefore 

 shafts must usually be sunk, into which the water will rise. This 

 is the case at Hinxworth, near Baldock, and many other places 

 where the geological conditions are the same. Care must be 

 taken not to sink for water where the lower greensand is absent, 

 as in many parts of Oxfordshire and the Vale of White Horse. 

 Instances of failure have occurred at Tetsworth, where the gault 

 rests on the Kimmeridge clay. 



As the gault clay underlies the escarpment of the upper green- 

 sand, or chalk, the most obvious source of Avater-supply to the 

 surface of the gault is from the springs which flow from, or generally 

 above the junction of these strata. Reservoirs might easily be 

 formed for whole districts by the common and united action ot 

 landowners to secure water of the best quality. Water rises by 

 gravitation from such a source to the top of Adwell House, near 

 Tetsworth. The town of Aylesbury is now seeking such a supply 

 from the chalk range near Tring. These valuable waters, which 

 might in many places be far more profitably used, now run into 

 the Ouse or the Thames. 



Next in order is the Kimmeridge clay. The same hindrance 

 as arises from the absence of the greensand below the gault is 

 found where the Kimmeridge rests on the Oxford clay. It was 

 by overlooking this fact that at least 2000/. was needlessly ex- 

 pended in boring a well, over 500 feet deep, at the Lunatic Asylum 

 near Aylesbury. At Abingdon there is an instance of water 

 obtained by boring through the Kimmeridge clay into the coral ine 

 oolite, the whole depth, partly into the latter stratum, being about 

 60 feet. The water is slightly impregnated with sulphuretted 

 hvdrog-en and iron, which it is believed is the case elsewhere. 

 It supplies a drinking-fountain in one of the back-streets of 

 Abingdon. 



No really successful instance of an artesian well in the Oxford 

 clay has fallen under my immediate observation. Its widely- 

 extended surface and position on the lower oolitic strata are 

 physical features which point to it as lacking good water, and as 

 likely to derive a supply by boring through it to the oolitic rock 



