IO 



ELEMENTS OF WATER BACTERIOLOGY. 



face of the earth. In the second place, during these 

 rainy seasons the amount of dissolved organic matter is 

 far greater than in summer, thus making the food-supply 

 of the bacteria more abundant. 



In standing waters all the tendencies which make for 

 the reduction of bacteria are intensified, and ponds and 

 lakes often give numbers under a hundred. The student 

 will find numerous analyses of natural waters in Frank- 

 land's classic work (Frankland, 1894). He notes, for 

 example, that the Lake of Lucerne contained 8 to 51 bac- 

 teria per c.c, Loch Katrine 74, and the Loch of Lintral- 

 then an average of 170. The water of Lake Champlain 

 examined by one of us (S. C. P.) in 1896 contained on 

 an average 82 bacteria per c.c. at a point more than two 

 miles out from the city of Burlington. Certain surface 

 water-supplies near Boston studied by Nibecker and one 

 of us (Winslow and Nibecker, 1903) gave the following 

 results: 



City. 



Wakefield.. 



Lynn 



Plymouth. 

 Cambridge 



Salem 



Medford. . 

 Taunton. .. 

 Peabody. . 



Number of 



Samples. 



Average 



Number 



of Bacteria 



per cc. 



59 

 16 



35 



94 



232 



524 



J 3 



141 



Russell found similar small numbers in sea-water at 

 Naples (Russell, 1891) and Wood's Hole (Russell, 1892). 



