MIRACLES OF SCIENCE 



with the apparatus are being made in France. The' 

 reason for this, Mr. Hewitt explains, is that his quartz 

 lamps are being extensively used in France in steriliz- 

 ing drinking water, and their efficacy in this connec- 

 tion led to the idea of a similar purification of milk. 



The French standards of purification for water are 

 gatifyingly different from those of some American 

 cities. The water is filtered and refiltered until it is 

 so nearly free from all impurities as to attain a de- 

 gree of transparency that permits print to be read with 

 a telescope through eight meters, or about 26 feet of 

 water. Even water of this degree of limpidity may 

 contain large numbers of bacteria. But when the 

 water has been caused to flow in a zigzag channel past 

 a large quartz lamp, specially devised for the purpose, 

 the germs thus acted on by the ultra violet rays are 

 found to be either dead or so devitalized that they 

 have very slight power of reproduction and hence 

 are innocuous. 



Should the present experiments prove conclusively 

 that all the bacteria in milk are similarly killed by the 

 ultra violet rays, the observation will be one of vast 

 practical importance, as means will be afforded of 

 sterilizing milk, which, it would seem, must be su- 

 perior to any previous method. For the moment, how- 

 ever, the familiar method of pasteurization, which 

 consists of heating milk to about 142 degrees Fahren- 

 heit for a period of three-quarters of an hour, is 

 the recognized method of rendering this beverage 

 wholesome. 



The pasteurization of milk is carried out on a very 

 large scale by our modern dairies. After being pas- 



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