163 
stration, that in the old epidemics, when the south-side of London 
suffered so dreadfully from cholera, the great cause of the mortality 
there was the badness of the water distributed in those districts 
of London. In the interval between the 1849 and the 1854 
' epidemics, one of the companies which supply the south side of 
London with water had amended its source of supply; it had gone 
higher up the river, and we at once lost a great part of the mortality 
on that side of the river. But it was found that this great difference . 
did not prevail uniformly through the south side of London, but 
was confined to those houses which were supplied from the 
amended source. There was still a great mortality on the south 
side of the river, but this belonged exclusively to the houses which 
were still supplied with impure water.” Again, he says, “The 
area of intense cholera in 1866 was almost exactly the area of the 
East London Water-supply.” 
During the period between the 1832 and the 1866 epidemics, 
the water-supply of the metropolis underwent important changes; 
and summarising the facts shown by the whole of the epidemics, 
we have figures as in 
TABLE I, 
Deaths from 
WATER SUPPLY Total Mortality | Cholera per 10,000 
from Cholera of Population 
Epidemic of 1832.—Polluted ... at 5,275 
Do. 1849.—Very much Polluted 14,137 
Do. 1854.—Less Polluted me 10, 738 
Do. 1866.—Much less Polluted... 5,596 
A very valuable report was made last August by Surgeon- 
Major Townsend, on an epidemic which visited the Central 
Provinces of India in the years 1875 and 1876. I shall give you 
his conclusions, because they are important in connection with the 
chemistry of the subject. He discards the theories usually held 
in that country as to atmospheric, fungoid, and miasmatic 
