1886.] NEW YORK ACADEMY OF SCIENCES. 51 



under a pressure of about eighty pounds to the square inch, 

 allowing it to escape through the reservoir, with this result: At 

 first there was no perceptible effect, but upon increasing the 

 amount of air supplied to the water, to the extent of about ten 

 per cent of the free air to an equal volume of water, the trouble 

 in the reservoir disappeared. Since that time, air has been freely 

 supplied whenever there appeared to be any recurreuee of the 

 growth of vegetation in the reservoir, and there has been no re- 

 turn of the offensive taste and smell. 



Kespectfully submitted, Chas. B. Brush, 



Con. Eng. Greenwood Cemetery. 



Similar troubles, and the development of a variety of odors 

 chronicled as "fishy," " pig-pen," " cucumber/' and the like, 

 have been reported as affecting, at one time or another, the 

 water supplies of most of our towns. There is good reason to 

 suppose that these complaints will continue as long as water 

 which, on standing, has lost most of its dissolved oxygen and has 

 become stagnant, is exposed to our burning suns, and allowed to 

 rise to a temperature of 70° and upwards, in uncovered reser- 

 voirs. Either it should be covered, so as to exclude light, and 

 kept cool, or, if its temperature is allowed to rise above 70° and 

 it is exposed to the sun, it should be charged with air and kept 

 moving. In our oion country, 2^'^'^vention of stagnation by 

 adopting the latter method has proven more economical and effi- 

 cient than the covering of the reservoirs. 



Before leaving this part of the subject, I shall state that when 

 I introduced the use of compressed air for water purification, I 

 did not do so for the reason that the air brought about a direct 

 chemical oxidation or burning up of the organic impurities. In 

 my various reports to the Water Department of Philadelphia, 

 relative to the new water supply of that city (volumes for the 

 year 1883, 1884, and 1885), and also to the Special "Water Com- 

 mission, appointed by the State of New York (1885), charged 

 with providing a new water supply for the city of Albany, I 

 have advocated the use of air under pressure for other reasons. 

 They were ; — Ist, Because the disagreeable taste and odor in 

 unpotable water are frequently due to gaseous and volatile im- 

 purities, which can be largely swept out of the water by the use 

 of an excess of air acting mechanically as a deodorizer and dis- 

 infectant, thereby exerting a sweetening action in the manner 

 of a water-scrubber ; x5d, because the chemical and biological 

 analyses contained in these reports show that where sewerage is 

 being broken down, it is in presence of large numbers of bacteria, 

 which grow and multiply upon a pabulum of sewage. Through 

 the agency of the vital processes of bacteria, oxygen is rapidly 

 absorbed and carried to the decomposing sewage which is broken 



