Clatification of the Public Water Supply of Cincinnati. 25 



dissolved in the water or swept into the currents in the solid state. 

 All of these act as precipitants of the organic matter in the water. 



This effect is strikingly ai)parent in the bright and sparkling 

 water produced in streams of small size when they are fed by the 

 waters of chalybeate springs. 



It is apparent in the rapid purification of all streams which are 

 the receptacles of sewage. The Oder River, wliich receives the 

 sewage of Breslau, practically i)urifies itself in fourteen kilometers 

 flow below the city. ' 



The waters of the Ohio River, after receiving the drainage of 

 an immense agricultural district and all of the sewage of tlie cit- 

 ies and towns on its banks and tributaries, comes to us in a purer 

 condition, so far as chemical analysis can now show, than that of 

 the water of the wells and springs on its banks and adjacent u})- 

 lands. 



The process of purification by fdtration, attended with the 

 action of coagulating material, is likewise in imitation of natural 

 processes. The surface water, contaminated with foul organic 

 matter, the detritus of vegetables and animal remains, when it sinks 

 into the ground comes in contact with the saline ingredients of the 

 soil, and its slimy albuminous matters are coagulated near the sur- 

 face, and as it sinks further through the earth, partly by oxidation, 

 partly by subsidation and straining, out, the impurities are left in 

 the rocky interstices, and the water, clarified and pure, issues in 

 the generous spring or the sparkling well. 



Tests of Precipitants Used in Subsiding Potatble Water. 



In the following tests, the sample of turbid water operated 

 upon was in each case one Liter, contained in a wide-mouthed 

 glass bottle with a glass stopper. The water stood in a column 

 about seven inches high and three inches in diameter. 



The precipitants were all dropped from the same Mohr's 

 Burette. 



The effect of the precipitants was observed by placing from 

 six to eleven bottles in a row, and adding to the second the mini- 

 mum amount estimated to produce an effect, and then adding to 

 the remainder amounts increasing in an arithmetical ratio. The 

 effects were then recorded at different times. 



It was determined that the hardness of the water of the vari- 

 ous samples would sufficiently show the chemical action. 



I. Dr. Franz Hulwa. Bicdermanus, Cent. BlaU, fur AgrigiUtur Chemic. 13-1. 



