B. P. I. 108. V. P. P. I. 118. 



A METHOD OF DESTROYING OR PREVENTING THE GROWTH OF 

 ALG^E AND CERTAIN PATHOGENIC BACTERIA IN WATER 

 SUPPLIES. 



INTRODUCTION. 



The necessity and importance of maintaining by every possible 

 means the purity and wholesomeness of public water supplies have 

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

 way serve as an additional safeguard against the pollution of reservoirs 

 or would prevent the bad effects produced by the growth of algae and 

 similar organisms. Although scientific men have been investigating 

 the various problems involved for a considerable length of time, it is 

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

 methods, and that, owing to the uncertainty of and disagreement among 

 eminent authorities, the whole question of water analysis, 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 vastly greater number of water supplies which 

 are rendered unfit for use, not because they are dangerous to public 

 health, but on account of the very offensive 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 really 

 confined to the last quarter of the nineteenth century, but only within 

 ten or fifteen years have we had any accurate knowledge of the effect 

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

 able that Dr. Hassall, of London, was the first to publish any adequate 

 account of a thorough microscopical examination of any water supply, 

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



