1 88 Elements of Water Bacteriology. 



The total number of bacteria and the number of colon 

 bacilli naturally vary widely in the sewages of different 

 cities and towns. European sewages, being more con- 

 centrated, show as a rule higher numbers than are found 

 in. America. Results compiled from various sources 

 show from one to five million bacteria in the sewages of 

 Essen, Berlin, Charlottenburg, Leeds, Exeter, Chorley, 

 and Oxford, two to ten millions in the sewages of Lon- 

 don, Walton and W. Derby, and over ten millions in the 

 sewages of Paris, Ballater and Belfast (Winslow, 1905). 

 The number of colon bacilli in English sewages varies 

 from 50,000 to 750,000. In American sewages, on the 

 other hand, bacteria are somewhat less numerous. At 

 Lawrence the determinations made from 1894 to 1901 

 showed on the average 2,800,000 bacteria per c.c. At 

 Worcester, Eddy reported 3,712,000 in 1901 (Eddy, 

 1902); at Ames, Iowa, Walker (1901) found 1,248,256 

 in the same year. At Columbus, Johnson (1905) reports 

 an average of 3,600,000 bacteria per cc; the individual 

 numbers varied from 320,600 to 27,000,000. The num- 

 ber of colon bacilli varied from 50,000 to 1,000,000 and 

 averaged 500,000. Day samples of Boston sewage col- 

 lected three times a week, from October, 1906, to April, 

 1907, showed an average of 1,200,000 bacteria per c.c. 

 In the summer months numbers are notably higher than 

 at other seasons in many sew-ages. Thus in 1903, Boston 

 sewage contained 2,995,000 bacteria in July, 4,263,600 in 

 August, 11,487,500 in September, 3,693,000 in October, 



