188 SCIENCE PROGRESS. 



microbes in the Thames flood water down to nearly the 

 minimum ever found in that river in dry weather, whilst, 

 by avoiding the first rush of each flood, a good chemical 

 quality could also be secured. 



There is, therefore, I think, a fair prospect that the 

 quantity of water derivable from the Thames at Hampton 

 could be increased from its present amount (120 millions of 

 gallons per diem) to 370 millions. 



Again, in the river Lea, although here the necessary 

 data for exact calculations are wanting, it may be assumed 

 that the present supply of 54 millions of gallons could 

 be increased by the storage of flood water to 100 

 millions per day. To these volumes must be added the 

 amount of deep-well water which is attainable from those 

 parts of the Thames basin which lie below Teddington Lock, 

 and in the Lea basin beloiv Lea Bridge, and which was 

 estimated by the last Royal Commission at rather more 

 than 67J millions of gallons. 



Thus we get the grand total of 53735- millions of 

 gallons of excellent water obtainable within the Thames 

 basin, the quality of which can be gradually improved, if it 

 be considered necessary, by pumping from the water bear- 

 ing strata above Teddington and Lea Bridge respectively, 

 instead of taking the total supply from the open rivers 

 above these points. Such a volume of water would scarcely 

 be required for the supply of the whole water area of Lon- 

 don at the end of fifty years from the present time, even 

 supposing the population to go on increasing at the same 

 rate as it did in the decade 1881-91, which is an assumption 

 scarcely likely to be verified. 



In conclusion, I have shown that the Thames basin can 

 furnish an ample supply for fifty or more years to come, 

 whilst the quality of the spring and deep-well waters and of 

 the filtered river water would be unimpeachable. To secure 

 these benefits for the future, storage must be gradually pro- 

 vided for 1 1,500 millions of gallons of flood water judiciously 

 selected in the Thames Valley, and a proportionate volume 

 in the basin of the Lea ; whilst filtration must be carried to 

 its utmost perfection by the use of finer sand than is at 



