The Bacteria in Natural Waters. 23 



bacteria to the cubic centimeter. Maschek (Maschek, 

 1887) found 36 wells out of 48 examined in Leitmeritz 

 which had a bacterial content of over 500 per c.c. Fischer 

 (Horrocks, 1901) reported 120 wells in Kiel which gave 

 over 500 bacteria per c.c. and only 51 with less than that 

 number. 



In the ordinary standard 48-hour period very few bac- 

 teria develop from normal spring-waters. Thus in an 

 examination of spring-waters made by the Massachusetts 

 State Board of Health in 1900 (Massachusetts State 

 Board of Health, 1901), of 37 springs which were prac- 

 tically unpolluted and had less than o.io parts per 100,000 

 excess of chlorine over the normal, 54 samples were exam- 

 ined and gave an average of 41 bacteria per c.c. Only 

 6 samples showed figures over 50. 



It now remains to consider the other great division of 

 ground-waters, namely, deep, "driven," or "tubular" 

 wells, which, if carefully constructed, should ordinarily be 

 free from all surface-water contamination, and should 

 show low bacterial counts. The results tabulated below 

 obtained by Houston in the examination of a series of deep 

 wells of high quality at Tunbridge Wells are fairly typical. 



BACTERIAL CONTENT OF DEEP WELL WATERS. 



(HOUSTON, 1903.) 



Bacteria per c.c. 



