166 ELEMENTS OF WATER BACTERIOLOGY 



bacilli in storage reservoirs and pipe systems may be 

 considerable. The figures obtained in 1900 at various 

 points in the distribution system may be cited as an 

 example. 



PERCENTAGE OF SAMPLES OF WATER CONTAINING 

 B. COLI. LAWRENCE, MASS. 



(Massachusetts State Board of Health, 1901) 



Fromme (1910) in the examination of a filtered 

 water averaging 35 bacteria per c.c. obtained the 

 following results in various quantities of water. 



PERCENTAGE OF SAMPLES OF WATER CONTAINING 

 B. COLI. 



(Fromme, 1910) 



In regard to the proportion of positive colon tests 

 permissible in a filter effluent, Clark and Gage (Clark 

 and Gage, 1900) reported some specially instructive 

 observations made when certain of the underdrains of 

 the Lawrence filter were relaid in the autumn of 1898. 

 In doing this work the sand on some of the beds was 

 seriously disturbed ; and in December, after the work was 

 completed, B. coli was found in i c.c. of the filtered 



