CONCLUSIONS. 41 



make these examinations as it now is to have a chemist or bacteriolo- 

 gist. In fact, in regions where the difficulty from algae is great, the 

 microscopical examination must take precedence of everything else as 

 a means of keeping the water palatable and satisfactory to the consumer. 

 In addition to the character of the organisms and the earliest possi- 

 ble determination of their appearance, it has already been pointed out 

 that the chemical constitution, the temperature, and other special con- 

 ditions of the water are factors in determining the line of treatment. 

 No specific instructions are given in this bulletin for the amount of 

 copper sulphate which is to be used for each species of algae which is 

 known to affect water supplies, because it is impossible to make a defi- 

 nite statement without a knowledge of the conditions already men 

 tioned. Each reservoir must be regarded as an individual case, re- 

 quiring special knowledge and a particular prescription. It is believed 

 that the public water supplies of this country are worthy of such spe- 

 cial care, and it would be a matter of regret if the method proposed 

 here should ever be regarded as a universal panacea to be used by 

 everyone, regardless of the organism to be eradicated and the condi- 

 tion of the water. 



APPLICATION OF METHOD FOR DESTRUCTION OF PATHOGENIC BACTERIA 

 NOT DESIGNED TO REPLACE EFFICIENT MEANS OF FILTRATION 

 ALREADY IN USE. 



The use of copper sulphate in clearing polluted reservoirs of patho- 

 genic bacteria, such as typhoid and cholera, is regarded as incidental 

 to the main purpose of the investigation. There already exists a most 

 efficient mean's of preventing the appearance of these organisms in 

 water supplies, and under no circumstances can it be considered that 

 the method as described is expected to replace or supersede slow sand 

 or any other efficient filtration. There are conditions, however, which 

 sometimes make it desirable to thoroughly sterilize a reservoir, and 

 under those circumstances the use of . copper sulphate is believed to 

 offer a new and adequate way of dealing with the difficulty. Expe- 

 rience has demonstrated the impossibility of compelling consumers of 

 what may be an infected water to boil it, or observe other precautionary 

 measures, and the absence of proper filtration plants in a very great 

 number of cities and towns in this country makes it necessary that 

 some efficient method for destroying disease germs in water be employed 

 until the danger from pollution be past. Up to this time no satisfac- 

 tory and yet harmless method has been known that would become 

 effective in the course of a very few hours and the cost of which was 

 in the reach of every community. It is believed that the results of 

 the experiments upon typhoid and cholera germs described in this 

 bulletin indicate that it will be possible under competent direction to 

 employ copper sulphate with perfect safety in any municipal water 



