1896.] on the Past, Present and Future Water Suj^phj of London. 55 



In every visitation of Asiatic cholera to London, the water supply 

 was either altogether unfilterecl or imperfectly filtered, besides being 

 derived from highly polluted parts of the Thames and Lea ; and the 

 enormous loss of life, amounting in the aggregate to nearly thirty-six 

 thousand peoj^le, can only be attributed to this cause ; for it has now 

 been abundantly proved that cholera is, practically, propagated by 

 drinking water alone, and that efiicient filtration is a j^erfect safeguard 

 against its propagation. Moreover, it is most satisfactory to know 

 that, since the year 1854, no case of Asiatic cholera in London has 

 been traced to the use of filtered river water. The following table 

 clearly indicates the close connection between intensity of pollution 

 and cholera mortality : — 



Cholera Epidemics in London. 



Epidemic of 1832 



„ 1849 



„ 1854 



„ „ 18G6 



Character of Water Supply as 

 regards Excremental Pollution. 



Polluted 



Very much polluted 

 Less polluted .. 

 Much less polluted 



Total :\Iortality 

 Irom Cholera. 



5,275 

 14,137 

 10,738 



5,596 



Mortality from 



Cholera per 10,000 



of Population. 



31-4 

 61-8 

 42-9 

 18-4 



These are the results arrived at by the most general investigation 

 of the subject. They show that in every epidemic, the mortality 

 varies directly with the intensity of the drainage pollution of the 

 water drunk by the people ; but, if time permitted, a more detailed 

 study of the statistics in these ejndemics would demonstrate, much more 

 conclusively, this connection between cholera mortality and the pollu- 

 tion of drinking water, a connection which has quite recently been 

 terribly emj^hasised in the case of Hamburg. 



Such is the verdict with regard to cholern, and the same is true 

 of that other great water-borne disease, typhoid fever. But, unlike 

 cholera, this disease is disseminated in several other ways, and its 

 presence or absence in any locality may not, of necessity, have any 

 connection with the drinking water, as is strikingly shown by the 

 health statistics of Manchester. 



There is no evidence whatever that, since the year 1869, when 

 typhoid fever appeared for the first time as a separate disease in the 

 liegistrar-General's reports, it has been conveyed by the water supply 

 of the metropolis. An inspection of the following diagram shows, 

 it is true, a greater proportional mortality during the period of 

 imperfect filtration than during the later period ; that is to say, from 

 1883, when the process began to be performed with uniform effi- 

 ciency ; but the plotting of a similar curve for the deaths by typhoid 

 in Manchester, shows that this disease arises from (jther causes than 

 polluted water, since the water supply of Manchester, derived as it 



