THE EFFECT OF ULTRA-VIOLET RAYS ON AMOEBA, 



AND THE USE OF THESE RADIATIONS IN 



THE STERILIZATION OF WATER. i 



By Weston P. Chamberlain and Edwaed B. Vedder,^ 



{From the United States Army Board for the Study of Tropical Diseases as they 

 Exist in the Philippine Islands.^) 



It has already been shown, by several investigators that the ultra-violet 

 rays of the spectrum are capable of killing bacteria in a few seconds, and 

 the .Westinghouse Cooper Hewitt Company of London and Paris have 

 constructed several types of practical water sterilizers utilizing these rays. 

 The ultra-violet radiation, upon which the action of these sterilizers de- 

 pends, is produced by a quartz mercury-vapor lamp either suspended 

 over or immersed in the water. One type has a capacity of 132,000 

 gallons (528,000 liters) of potable water in twenty-four hours, and only 

 requires an electric current of three or three and one-half amperes at 220 

 volts for its operation. It has been demonstrated by experimentally pol- 

 luting water with Bacillus coli that these organisms are killed during the 

 passage through such a sterilizer, although the water remains in the ap- 

 paratus for only five seconds. A more complete description, together with 

 photographs and diagrams of this apparatus, may be obtained from the 

 articles of Poulds(l) and Thresh and Beale. (2) 



There are many features about this method of sterilization that render 

 it peculiarly suitable for use in tropical countries and by armies in the 

 field, among which the following may be mentioned. It is automatic 

 and can be intrusted to a comparatively unskilled man, this automatic 

 action being secured by a valve in the inlet which is operated by the 

 current of the same circuit that produces the rays, and which prevents 



* Published by permission of the Chief Surgeon, Philippines Division. 



'W. P. Chamberlain, major, Medical Corps, United States Army, and E. B. 

 Vedder, captain, Medical Corps, United States Army, members of the United 

 States Army Board for the Study of Tropical Diseases as they Exist in the 

 Philippine Islands. 



' The apparatus for these experiments was supplied by the Bureau of Science, 

 and the exposures were made in that Bureau. 



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