24 



Elements of Water Bacteriology. 



Fifteen driven wells in the neighborhood of Boston, ex- 

 amined in 1903, showed at the end of 48 hours an average 

 of only 18 colonies per cc; and the results of certain 

 examinations of other wells and springs, recently made 

 by the authors, are given in the table below. 



BACTERIA IN DEEP WELL AND SPRING WATERS. 



It is plain that water absolutely free from bacteria is 

 not ordinarily obtained from any source. In deep wells, 

 however, their number is small; and the peculiar character 

 of the organisms present is manifested in many caseg by 

 the slow development at room temperature (frequently no 

 growth until the third day), the entire absence of Uquefying 

 colonies, and the abundance of chromogenic species. 



