SYMPOSIUM ON PUBLIC HEALTH PROBLEMS 91 
buildings in Hamburg housing 400 people, and supplied with 
water from Altona. These people were exempt from the 
disease. As in the case of all communicable diseases, its rav- 
ages were not confined to Hamburg, but tongues of the out- 
break shot out to other places and even reached the port of 
New York. 
Stimulated by the example of the Hamburg epidemic, there 
developed a movement in the United States for better water 
supplies, and it also caused certain legislatures, notably that 
of Ohio, to empower state boards of health with authority to 
supervise the installation of water supplies with a view to pro- 
tecting the public health. 
The early filtration works were of the so-called slow sand 
type, and were extensive in area, costly to build, and not readily 
adaptable to the treatment of very turbid waters. American in- 
genuity came to the rescue of this situation in the early 80’s 
by the invention of the so-called rapid sand filter, assisted by 
preliminary chemical coagulation. These filters were able to 
give good results when operated at rates approximately forty 
times as great as rates permissible with the slow sand filters, 
Because of their small size, it was practicable to introduce 
means for flushing the filters, thereby thoroughly cleaning the 
sand at frequent intervals. 
At first these filters were regarded with skepticism by en- 
gineers, but a series of experiments in Louisville, Kentucky, in 
1897, conducted by Fuller, showed that when correctly de- 
signed, they could produce results equal to those obtainable 
with slow sand filters, and moreover they could handle waters 
of very high turbidity. Rapid sand filters were thus firmly 
established as an acceptable and satisfactory means for the 
treatment of municipal water supplies. 
Following the Louisville experiments numerous filtration 
plants were installed in various cities of the United States, all 
of which, unfortunately, were not efficiently designed, or 
efficiently operated. Even the poorest, however, unquestion- 
ably constituted a great protection to the public health, and 
assisted in the growing movement for purified water supplies. 
It is but proper that acknowledgment be made to the various 
filter companies that built and installed these filters for much 
