i6 



ELEMENTS OF WATER BACTERIOLOGY. 



in Kiel which gave over 500 bacteria per c.c. and only 51 

 with less than that number. 



Several unpolluted springs and open wells were ex- 

 amined by Sedgwick and one of us (Sedgwick and Pres- 

 cott, 1895) with the following result: 



Spring No. i. 252, 255, 258 bacteria per c.c. 



" 2. 163, 149, 134 



' 3- 92, 98, 105 



" " 4- 95> 101, 106 



" " 5. 193, 213, 218 



" "6. 216, 208, 201 



OPEN WELLS. 



No. i. 509, 525 bacteria per c.c. 



" 2. 248, 190 " 



" 3- 602, 560 " 



" 4- 335> 332 " 



" 5. 2084, 2063, 2287 bacteria per c.c. 



" 6. 8905, 8905, 8640 



" 7. 702, 910, 871 



" 8. 720, 712, 763 



It should be noted that the above results were obtained 

 by incubating the plates for considerable periods of time. 

 In the ordinary standard 48-hour period but very few 

 bacteria develop from normal ground-waters. Thus in 

 an examination of spring-waters made by the Massa- 

 chusetts State Board of Health in 1900 (Massachusetts 

 State Board of Health, 1901), of 37 springs which were 

 practically unpolluted and had less than 10 parts per 

 100,000 excess of chlorine over the normal, 54 samples 

 were examined and gave an average of 41 bacteria per 

 c.c. Only 6 samples showed figures over 50. On the 

 other hand, the analysis of the bottled samples of the 

 same waters as sold after exposure to contamination in 



