BACTERIA OF WATER AND SEWAGE 299 



above the city, the water was used in a raw state. Altona. 

 on the other hand, was obliged to take its water, if at all, from 

 th's river, after the sewage of 800,000 people had been poured 

 L; Lo it. The water was therefore filtered. In 1893, during the 

 cholera epidemic, the cases were very frequent in Hamburg, 

 where raw water was used, and very few in number in Altona, 

 where filtered water was used. The character of the water 

 supply was the only difference between these two places which 

 could account for the distribution of the cases. To complete 

 the proof that this Hamburg epidemic was water-borne, in the 

 winter, after the disease had disappeared from Hamburg, 

 it broke out explosively in Altona, because, as was later 

 ascertained, the sand filter had cracked on freezing, allowing 

 the unfiltered water to pass into the city main. 



Water Analysis. The efficiency of the bacteriological 

 water analysis is becoming more and more evident as its use in- 

 creases and the technique becomes perfected. Its value, sup- 

 plementing that of a chemical analysis, was first demonstrated 

 by Frankland's work on the filtered water of London. Chemi- 

 cal analysis was unable to detect the purification accomplished 

 by a sand filter, and these filters were about to be discarded 

 in London as inefficient when Frankland showed that so far 

 as the removal of bacteria was concerned, their efficiency was 

 very high, i.e. over ninety-nine per cent. Filters can only be 

 efficiently controlled by proper bacteriological analyses. In the 

 sanitary examination of water, the bacteriological determina- 

 tions are becoming recognized as of great value. In a bacterio- 



