350 



SCIENCE OF HOME AND COMMUNITY 



situation. They found that the currents of the lake were 

 carrying some of the sewage, containing its typhoid fever 

 germs, to the part of the lake from which water was taken 

 for drinking. So the city had the inlet for the water ex- 

 tended miles out into the lake, and the outlet for the sewers 

 placed at such a distance from the intake that the sewage 

 could not reach it. As soon as this work was completed, 

 the number of cases of typhoid fever decreased at once and 



20 



1887 



1890 



1895 



1900 



1905 



1910 1912 



FIG. 144. Effect of filtering water on typhoid death rate. 



within a year the number of deaths was only one eighth as 

 many. 



Lawrence, Mass. Lawrence is situated on the Merrimac 

 River. Nine miles above on the same river is the city -of 

 Lowell, and above Lowell are still other cities. Each of 

 these cities takes its drinking water from the river above it 

 and pours its sewage into the river below it. Thus each 

 city gets in its drinking water some r of the sewage of the 

 cities above it. The lower cities on the river were especially 

 subject to typhoid fever. Whenever Lowell had an out- 



