BACTERIA IN THE INDUSTRIES 177 



attention within recent years. Perhaps the best reference work on this 

 phase of water analysis is that by Whipple (Microscopy of Drinking Water. 

 John Wiley and Sons, 1919) to which the student is referred. An excellent 

 work on water bacteria is that by Prescott and Winslow (Elements of 

 Water Bacteriology. John Wiley and Sons, 1913). Most of the authori- 

 tative works on general hygiene contain a brief mention of the micro- 

 scopical as well as bacteriological examination of water supplies. 



Even the most casual observation will make it clear that the study 

 of water supplies forms the very groundwork of sanitary science. Not 

 only is it important to study the 'water intended for drinking purposes, 

 but also the water supplies used for irrigating purposes, the sewage waters, 

 rivers, lakes, ponds, ditches, water of swamp lands, etc. 



A. Water Analysis. Water and food are the absolute essentials to 

 life, and of these two, water is the more important. The water supply 

 must be ample and must be of good quality. Water for drinking, cooking 

 washing and bathing purposes must be free from harmful or otherwise 

 objectionable ingredients. The water supplies intended for drinking 

 purposes must be free from sewage contaminations and must not contain 

 any poisons (chemical, vegetable, or animal) which might prove harmful. 

 The importance of abundant pure drinking water cannot be too strongly 

 emphasized. An abundant supply must be at hand or immediately 

 available at all times. All possible desirable sources of drinking water 

 must be carefully investigated and examined, and the supplies well 

 guarded and none allowed to be used for other than drinking purposes, 

 until that one all-important need is liberally supplied and future require- 

 ments assured. 



Streams, large and small, lakes, ponds, wells and springs, are the main 

 sources of drinking water. As a rule deep wells and deep source springs 

 furnish the best drinking water, and shallow pools and small streams the 

 poorest, considered from the standpoint of possible harmful contamination. 

 Lakes and larger streams assure an ample supply and the quality may be 

 fair or even very good. Mountain streams feel by melting glaciers and 

 snow, furnish good water. 



Four methods are employed in the examination of water, the organo- 

 leptic, the microscopical, the bacteriological, and the chemical. Each 

 method has its special merits and all four are essential. 



As to the organoleptic tests, water may be wholly colorless or clear; it 

 may be turbid due to fine sand or silt and clay or dirt; it may be yellowish 

 turbid due to fine clay; it may be a yellowish lemon tinge due to diatoms; 

 or greenish due to nostoc, oscillaria and other algae; it may be brown or 

 flocculent brown due to iron fungi (Leptothrix and algae) ; or it may be 

 wine colored due to peat; etc. It may be and should be odorless. Rain 



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