PREFACE. 



The necessity of finding some cheap and practical method of prevent- 

 ing or removing algal contamination of cress beds first led this Office 

 to undertake the investigations described in this bulletin. The success 

 of the first experiments in 1901 was so marked that it seemed wise to 

 extend the work, and authority was, therefore, granted by Congress 

 "to study and find methods for preventing the algal and other con- 

 taminations of water supplies." 



The progress of the investigation has been noted from time to time 

 in the annual reports of the Bureau. Though the work is not yet com- 

 pleted, we have been urged to publish the results already obtained for 

 the consideration of boards of health and officers in charge of public 

 water supplies. 



Doctor Moore and Mr. Kellerman have shown that it is entirely 

 practicable to cheaply and quickly destroy objectionable alga? in small 

 lakes, ponds, storage reservoirs, and other similar bodies of water by 

 the use of extremely dilute solutions of copper sulphate or of metallic 

 copper. The fact that an extremely dilute solution (one to one 

 hundred thousand) will also destroy the most virulent typhoid and 

 cholera bacteria at ordinary temperatures in three hours is of great 

 importance and significance. Solutions of copper as dilute as this 

 are not considered injurious to man or other animals. The value of 

 copper, especially colloidal, in preventing or treating typhoid and 

 other related diseases should be carefully investigated by competent 

 pathologists. 



We desire it distinctly understood that, so far as bacterial contami- 

 nation of water is concerned, the methods here proposed are not to 

 take the place of, but are simply to supplement the standard methods 

 of filtration; neither can too much stress be laid upon the importance 

 of the consumer boiling water to be used for drinking purposes when 

 taken from a contaminated source. 



Upon application to the Department by proper authorities, infor- 

 mation and assistance will be furnished in determining the organisms 

 causing the trouble in cases of algal pollution, and the proper treat- 

 ment will be recommended. Jt is earnestly hoped that no test of the 

 method described here will be made without first consulting the 

 Department. 



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