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lation. This is a very difficult as well as a very essential 

 part of the operation and many mechanical devices are 

 in use to perform this duty. The principle of applying 

 a substance to water for the purpose of coagulating its 

 impurities is not patentable for it has been in use, as 

 before stated, for centuries. But the various devices for 

 regulating the strength of the solution and of propor- 

 tioning the supply to the volume of influent water are 

 the subjects of many patents. 



In 1890 forty-three public water supplies were said to 

 be using this method of filtration. I have received 

 statements from officials where it was in use expressing 

 great satisfaction with the results obtained. Eminent 

 authorities express their approval of the process. 



In 1887 the city of Newburgh was considering the 

 matter of improving its water supply and the manu- 

 facturers of a mechanical filter plant proposed a method 

 of purification involving the use of their filter with sub- 

 sequent seration. The proposition was regarded favor- 

 ably by the water board, who employed Prof. C. F. 

 Chandler to investigate and report upon its adaptability 

 to their case. His report stated that experiments made 

 with the water supplied to Newburgh showed that the 

 plan proposed was "simple, efficient and economical, and 

 that no objections whatever can be found to it on sani- 

 tary grounds." The plan was not, however, adopted. 

 Prof. A. R. Leeds is an ardent advocate of this method 

 of purification, although it should be stated in this con- 

 nection that he is also a director in one of the companies 

 manufacturing filters of this class. Nevertheless I be- 

 lieve that his analyses of water and opinion based there- 

 on can be relied upon. 



In regard to a sample of water from Cincinnati, Ohio, 

 before and after treatment with this process, he says : 

 "The change from a dirty, opaque, turbid water — with 

 strong taste and smell — to a colorless, palatable water, 



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