QUANTITATIVE BACTERIOLOGICAL ANALYSIS. 27 



water plated out in gelatine. The following results were 

 obtained : 



Plotzen Lake on September 19, 1885 . . 490 organisms per c.c. 



October 5, 1885 . . . 4,900 



Kiver Spree on May 17, 1886 . , 171 , 



' .' . . 1,780 



Wei'ssen Lake . . . . , , 735 



Pond water ....... 14,400 



Hail. Buj wid and Foutin investigated the bacterial contents 

 of hailstones. In a very large stone 21,000 organisms per c.c. 

 were found, but in a smaller one, about the size of a walnut, only 

 729 bacteria per c.c. were counted. 



Rain. Very few bacteriological examinations of rain have 

 been made. Miquel, at Mountsouris, found the bacteria to 

 average 4'3 per c.c. during the years 1883-1886. In the middle 

 of Paris 19 bacteria per c.c. were found. 



Rivers. The Thames and Lea were examined by Frankland 

 for each month during the years 1886, 1887, and 1888. The 

 following table gives the number of bacteria found in Thames 

 water collected at Hampton. 



Micro-organisms per c.c 

 Month. 



January . 



February . 



March 



April 



May 



June 



July 



August 



September 



October . 



November 



December 



Similar results were obtained with water from the Lea. Both 

 rivers contained fewer bacteria during the summer months. 

 This is due to the fact that in the summer the rivers are chiefly 

 dependent on springs for supply, while in the winter they 

 receive surface washings from cultivated land. 



Miquel examined the Seine, Marne, and Ourcq, and found the 



