CHAS. E. FOWLER. 273 



On the principle that " an ounce of prevention is 

 worth a pound of cure" the negative method of purifi- 

 cation, by prevention of pollution, adopted by the city 

 of New York, should take a high rank in methods of 

 water improvement. The supi)ly of New York is drawn 

 mainly from the water shed of the Croton River. This 

 water shed comprises within its limits a number of vil- 

 lages and a few manufactories. The entire area is under 

 surveillance, and under a special enactment of the State 

 Legislature, every objectionable feature, artificial or nat- 

 ural, has been or is being removed from within a dis- 

 tance of 250 feet from every stream, pond, or reservoir 

 therein. The village of Carmel consisted of a principal 

 street running north and south near the easterly shore 

 of Lake Glenida. within the Croton water shed, its outlet 

 forming a tributary to the middle branch of Croton 

 River. Houses were located on both sides of this street, 

 those on the westerly side being within the prescribed 

 distance. They were consequently ordered removed, and 

 now a beautiful lawn has taken their place. Through- 

 out the entire Croton basin above Croton dam this pro- 

 cess of removal has taken place in greater or less degree 

 until the waters are as free from contamination by refuse 

 from human habitations or industries as they well can 

 be. Watch is also maintained to prevent any encroach- 

 ment upon this prescribed limit. 



The simplest method of direct purification is by sedi- 

 mentation, by the use of settling basins or their equiva- 

 lent. The efficiency depends upon the character of the 

 substances in suspension, little or no effect being had 

 upon matters in solution, and the length of time avail- 

 able for deposition. It has been stated that even bacte- 

 ria are subject to the laws of subsidence, and gradually 

 pass to the bottom, so that, with sufficient time, varying 

 from a few days to many months, almost any water may 

 be rendered safe for use by simply standing quiet in a 



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