BACTERIA AND ICE 155 



direction are limited, and that the fact of water 

 being frozen does not necessarily convert a bad 

 water into immaculate ice. 



It is worthy of note that the city of Lawrence, 

 in Massachusetts, obtains the greater portion of its 

 ice from a river which in its raw, unpurified condi- 

 tion was rejected for purposes of water-supply in 

 consequence of the numerous and severe epidemics 

 of typhoid fever which accompanied its use. Since 

 the application of sand-filtration to this water, 

 however, the death-rate from typhoid in this city, 

 instead of being abnormally high, has fallen 

 abnormally low, and this improvement is attri- 

 buted to the excellent quality of the water sup- 

 plied to the city, and has taken place despite the 

 use which still continues of ice from the polluted 

 river. The authorities consider the city's immunity 

 from typhoid amply justifies their sanctioning the 

 distribution of this river-ice, the freezing of the 

 water having rendered it sufficiently pure to re- 

 move all danger to health from its consumption. 



So far we have been considering the effect on 

 bacteria of freezing carried on under more or less 

 natural conditions; but much interesting work of 

 a more detailed character has been carried out 

 with reference to the behaviour of particular 

 varieties of micro-organisms when frozen under 

 more or less artificial conditions. 



