THE WATER SUPPLY OF LONDON. 187 



974 millions of gallons, and this number does not in- 

 clude the 1 20 millions daily abstracted by the five London 

 Water Companies who draw their supplies from the 

 Thames. 



Thus, in round numbers, we may say that after the 

 present wants of London have been supplied from this 

 river, there is a daily average of nearly 1000 millions of 

 gallons to spare. Surely it is not too violent an assumption 

 to make that the enterprising engineers of this country can 

 find the means of abstracting and storing for the necessary 

 time one-fourth of this volume. 



As regards the quality of this stored water, all my 

 examinations, of the effect of storage upon the chemical and 

 especially upon the bacterial quality, point to the conclusion 

 that it would be excellent. Indeed the bacterial improve- 

 ment of river water by storage for even a few days is 

 beyond all expectation. Thus the storage of Thames water 

 by the Chelsea Company for only thirteen days reduces 

 the number of microbes to one-fifth the original amount, 

 and the storage of the river Lea water for fifteen days, 

 by the East London Company, reduces the number on the 

 average from 9240 to i860 per cubic centimetre or to one- 

 fifth ; and lastly, the water of the New River Cut, con- 

 taining on the average 4270 microbes per cubic centimetre 

 contains, after storage for less than five days, only 18 10, 

 the reduction here being not so great, partly on account 

 of the shorter storage, but chiefly because the New River 

 Cut above the point at which the samples were taken, is 

 itself a storage reservoir containing many days' supply after 

 filtration. Indeed quietness in a subsidence reservoir is, 

 very curiously, far more fatal to bacterial life than the most 

 violent agitation in contact with atmospheric air ; for the 

 microbes which are sent into the river above the falls of 

 Niagara, by the City of Buffalo, seem to take little or no 

 harm from that tremendous leap and turmoil of waters, 

 whilst they subsequently, very soon, almost entirely dis- 

 appear in Lake Ontario. 



It is not, therefore, too much to expect that storage for, 

 say a couple of months, would reduce the number of 



