MICROORGANISMS IN WATER. 



197 



Average annual death rate from typhoid fever per 100,000 of the population. 



8 16 24 32 40 48 56 64 72 80 88 96 104 112 120 DEATHS 



SPRIN6FIELD 

 WILMINGTON 



An instructive contrast between Altona'and Hamburg before the latter 

 filtered its water, having learnt its lesson from a sharp outbreak of cholera. 



A FEW 

 SCATTERED CASES Of 



ALTOHA^ 



HAMBURG. 



POPULATION: 600.000 

 CHOLERA CASES'. 17.000 



DEATHS: 8.600 



ALTONA: 



WATER FILTERED 



HAMBURG: 



WATER. UMFILTERED 



FIG. 57. (After G. E. Armstrong.) 



