B. P. 1.-103. V. 1'. r. l.-ll«. 



A METHOD OF DRSTfloVINd 0I{ PREVRNTINO THE UUOWTIl OF 

 AL(J;E AND CFUTAliN I'ATIKMiFNK' IJACTFUIA IN WATER 

 SUPPLIES. 



INTRODUCTION. 



The necessity and importance of inaintainintj: ])y every possil)lc 

 means the purity and wliolesomeness of public water supj[)lies have 

 caused those in authority to welcome a method which wouUl in any 

 wa}' serve as an additional safefjuard aii'ainst the pollution of reservoirs 

 or would prevent the had etiects produced hy th(> jirowth of alo-ic and 

 similar organisms. Although scientific mi-n have been investigating- 

 the various problems involved for a consideral)le length of time, it is 

 feared that the publie has not always been in sympathy with these 

 methods, and that, owing to the uncertaintv of and disagreementamong 

 eminent authorities, the whole question of water anah^sis, both chem- 

 ical and bacteriological, has come somewhat into disrepute. 



MICROSCOPICAL EXAMINATION OF DRINKING WATER. 



While the best known cases of water pollution are those due to the 

 presence of typhoid and other germs which have given rise to serious 

 epidemics, there are a vastlv g'reater number of water supplies which 

 are rendered unfit for use, not because they are dangerous to pid)lic 

 health, but on account of the very oti'ensive odor and taste produced 

 in them by plants other than bacteria. For this reason, in recent 

 years, the question of whether or not a water was fit to drink has been 

 submitted to the biologists as well as to the chemists and bacteriol- 

 ogists, a biological examination being- generally understood to mean 

 the determination of the character and quantity of the microscopical 

 plants and animals the water may contain as distinct from the bacteria. 



The history of this method of examining drinking water is reall}^ 

 confined to the last quarter of the nineteenth century, but onl}^ within 

 ten or fifteen yeai's have we had any accurate knowledge of the efl'ect 

 of these minute plants upon the water in which they live. It is prob- 

 able that Dr. Hassall, of London, was the first to pu])lish any adequate 

 account of a thorough microscopical examination of any water supply, 

 and this work, which appeared in 1850, was practically the only thing 



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