THE WATER SUPPLY OF LONDON. 



185 



analysed samples of the water. The results, in a very con- 

 densed form, are recorded in the annexed Table. Twenty- 



SPRING AND DEEP-WELL WATERS IN THE THAMES 



BASIN. 



one samples of Oolitic spring - water were analysed, and 

 every one of these was of even greater organic purity 

 than 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 increased in amount, whilst 

 the hardness is much mitigated, owing to the replacement 

 of bicarbonate 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 



