56 J. HOPKINSON HERTFORBSHTEE RAINFALL, 



eventually intersect the cone of exhaustion of the other. It may 

 also be a long time before the abstraction of water from a deep well 

 affects the flow of an adjoining stream on the Chalk, but that it 

 must eventually do so is certain. 



If, however, the water raised be used in the district from which 

 it is obtained, that is to say, if it be not conveyed away to a 

 distance, as from the Colne Valley or the Lea Valley to London, 

 the river flowing by on the Chalk will only be depleted above the 

 point of abstraction, for all the water raised from the Chalk will 

 be returned to the river, the greater part probably as effluent water 

 from sewage. The water we raise in Hertfordshire for the supply 

 of our towns, except the comparatively small amount sent away 

 by brewers and mineral-water manufacturers, does not reduce the 

 volume of the Colne and Lea below the points where they leave 

 our county, so that we only take what is our own, and we restore 

 it after we have made use of it, robbing no one. If it be taken 

 from us and conveyed to London, it is sent into the Thames below 

 London ; our rivers are completely robbed of it ; and their volume 

 below the points of intake, if the water be taken directly from the 

 rivers, and both above and below, if it be taken from the Chalk, 

 will be permanently reduced. 



