THE MICROBES OF WATER 293 



sample should be violently shaken to ensure an even 

 distribution of the microbes throughout the water. 



By using Koch's or the plate-cultivation method, 

 the author l obtained the following average number 

 of microbes (colonies) in 1 cc.of a sample of water from 

 theriverWitham(at Lincoln) during the year 1887 : 



January, . . 2,016 



February, . 3,488 



March, . . 10,287 



April, . . 11,692 



May, . . 11,923 



June, . . 12,000 



July, . . 10,184 

 August, . 



September, . 4,110 



October, . . 9,621 



November, . 10,211 



December, . 9,787 



These figures (monthly means) give a yearly 

 mean of 8665 microbes in 1 cc., or quarterly means 

 as follows : 



Spring, . . - . . . . . 11,300 



Summer, .-V . ... . 11,092 



Autumn, . . . . . . . 7,980 



Winter, . ... .-. ... ... . 5,097 



From these results the greater number of microbes 

 in the Witham were during the spring and summer. 

 Another series of experiments with water from 

 certain rivers gave the following results : Witham, 

 11,860; Irwell, 9230; Thames, 25,745; and the 

 Seine, 56,219 microbes per cubic centimetre. 



Dr. P. F. Frankland 2 has made periodical exami- 

 nations of the river and well waters from which 

 the water-supply of London is derived ; and during 

 the year 1886, he obtained the following number of 

 colonies (on gelatine-plates) per 1 cc. of water : 



1 Griffiths' Researches on Micro-Organisms, p. 77. 



2 Journal of Society of Chemical Industry, vol. iv. (1885), and 

 vol. vi. (1887); Transactions of Sanitary Institute, vols. viii. and 

 ix. ; Proc. Roy. Soc., 1885; and Proc. Inst. of Civil Engineers, 

 1886. 



