The Birmingham age-herald., 1914-11-01

gas was touched Off.
 Therefore, there are two systems. one containing pure water and the other dangerous water. This Is not a prac- tice to any great extent.
 Large streams, rivers, natural lakes and artificial lakes are generally employed All these arc more or less polluted. The farther down the stream and the smaller the lake the greater the danger. It Is said that typhoid germs will live in these waters about five days. Weter that flows leo miles a day will flow in five days 800 miles, and is therefore dangerous for that distance from the point of pollution and infection. In thickly settled communities the streams are greatly polluted and in- fected with disease producing germs, par ticularly typhoid fever Into these streams flow the surface water when it rains, and Into which are empted the sewage of cities. When the water is de- rived from large, deep lake 1t is safe If the intake pipe Is far out In the lake, beyond the possibility of contamination for example, Chicago. Which city, how ever. drains its sewage, ultimately. into the Mississippi river. thus avoiding pol lution of Lake Michigan, the source of its water supply. Public water from streams, small lakes, the catchment ba- sins as a rule is impure, and must be artificially treated to be wholesome and safe. When the stream is large the water may be obtained from its natural chan nel When too small for this, the stream must be damned; if the volume of water in the stream Is too little. large catch ment basins must be provided so as to impound the water. This Is perhaps the best method, because a large collection Of still water affords the best conditions for sedimentation and bacterial antag- cnism in which is destroyed most of the disease producing germs by the sapro- r''tes O. non-disease producing germs. The objection, however, Is that such wa ter is the growing place for algae, dis tomas, protozoa and other microscopic beings, which may affect the water caus- ing bad taste and smells. "Odors in wa ter are objectionable rather than detri- mental to health," Roseneau. These dis agreeable odors and taste originate from the putrefaction of organic matter The inipounding basins are generally formed by damming a small stream in a narrow valley. Uake Purdy Is a familiar ex- ample.)
 Artificial Purification
 First. Sediment or settling basins. the principle employed being gravity; sec olid, coagulation, using some harmless coagulant, which groups the solid matter into little bodies in which many bacteria are enclosed and fall to the bottom; third filtration through gravel and sand, a kind cc artificial ground soil thus straining out small particles of. matter; fourth, chemi- cal disinfection by the use of a safe dis infectant--for example. hypochrlorite of lime. solutions of which are mixed with the finished water.
 Examination of Water
 This is physical. chemical and micro scopic. By the first the gross character of the water Is learned by the second It's chemical contamination; by the third the presence of bateria are determined.
 The vast majority of water borne dis eases are polluted with the excrement of Inan and animals. and as the colon bacilli., harmless organism in the water. comes from the intestines of man and animals their presence in water is proof posi- tive of intestinal pollution, and they are the criterion by which such pollution is determined. When found in water we know that it has been polluted with human and animal exrement, and 1t is a logical conclusion that disease germs and ra rasites that pass out of the intestines cf animal and man may also be present. If found in considerable numbers the water is unsafe. Whenever there is doubt as to the purity and non-infectious quail ity of the water there is at hand in every home sure means of disinfection. to-wit. boiling. and this should always he done before 1t ia swallowed.
 Tn the next bulletin Air" will be dis cussed. R. M. CUNNINGHAM.
 City Hsalth onicsr.