BACTERIOLOGY AND WATER 95 



systematically applied for the first time to the 

 London water-supply by Professor Percy Frank- 

 land, and the entirely unexpected result obtained, 

 that whereas the River Thames water at Hampton 

 contained as many as 1,644 micro-organisms in 

 about twenty drops, this water, after passing 

 through the sand-filters, possessed as few as 

 thirteen in the same number of drops. The re- 

 markable purification effected in the treatment of 

 the water was thus very clearly shown, and an 

 entirely new aspect was given to the processes 

 of sand-filtration. 



The importance of these results was quickly 

 appreciated by the official water-examiner, the 

 late Sir Francis Bolton, and at the request of 

 the Local Government Board regular monthly 

 bacteriological examinations of the London water- 

 supply were conducted. 



It is amusing to recall that, at the time when 

 these results were first published, the public, 

 instead of being reassured by these facts, were 

 greatly alarmed, and it is a matter of history 

 that the mere demonstration of the presence of 

 micro-organisms in drinking-water caused a fall 

 in the price of several of the water companies' 

 stocks ! 



These investigations, which have since been 

 confirmed by others both in this country and 



