1896.] on the Past, Present and Future Water Supphj of London. 71 



Spring and Deep-Well Waters in the Thames Basin. 



Twenty-one samples of oolitic spring water were analysed, and 

 every one of these was of even greater organic purity tban the water 

 delivered by the Kent company, which I have always regarded as the 

 standard of organic purity to be aimed at in all other water-works. 



Five springs issuing from the lower greensand were examined, 

 and again every one of these was of even greater purity, organically, 

 than the Kent company's water ; whilst they were, on the average, 

 only one-third as hard. Forty-six samples of water from the chalk 

 were chemically examined, and these also contained but the merest 

 traces of organic matter. 



All these samples from the chalk were derived from sources 

 where the water-bearing stratum is free from a covering of London 

 clay ; but as soon as the chalk dips beneath the London tertiary sands 

 and clay, the quality of the water undergoes a remarkable alteration. 

 The total solids in solution are greatly incrensed in amount, whilst 

 the hardness is much mitigated, owing to the replacement of bicar- 

 bonate of lime by bicarbonate of soda. These waters are also of 

 high organic purity ; but, as the quantity is very limited, it is useless 

 to dwell upon them. They supply the Trafalgar Square fountains 

 and the London breweries, and we can well aflord to leave them to be 

 converted into beer. For dietetic purposes, there is no better water 

 in the kingdom than the underground water of the Thames basin. 

 For sentimental reasons, I should like to see it conveyed to the works 

 of the various companies in special conduits ; but we have seen that, 

 on hygienic grounds, it may safely be allowed to flow down the bed of 

 the Thames, if it be afterwards efficiently filtered. 



So much for quality, now as to quantity. The basins of the 

 Thames and Lea include an area of upwards of five thousand square 

 miles. Of this, rather more than one-half, including the oolitic, 

 cretaceous, and portions of the tertiary formations, is covered by a 

 porous soil upon a permeable water-bearing stratum. The remainder 

 is occupied by the Oxford, Kimmeridge, Gault and London clays, 

 being thus covered by a clay soil upon a stiff and impervious subsoil. 



