CONCLUSIONS. 41 



make thoso cxaniiiiutions as it now is to have a elieinist or l)at't(M-iolo- 

 ^•ist. In Fact, in regions where the dilhculty from al^iv is ^reat, the 

 microscopical examination must take })reee(hMicc of overvtliing- else as 

 a means of keepin*;the water palatable and satisfactory to the consumer. 

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

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

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

 ditions of the water are factors in determinino- 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 ali;je which is 

 known to atl'ect water supplies, because it is impossible to make a defi- 

 nite statement without a knowledoe of the conditions alreadv men 

 tioned. Ji}ich reservoir muxt he regarded as an indivldiial ease, re- 

 quiring special hnmvledge and a i^articular prescription. It is 1)elie\'ed 

 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 

 ev^ervone, regardless of the organism to bo erndicat(>d and the condi- 

 tion of the water. 



APrLICATION OF METHOD FOR DESTRUCTION OF I'ATIIOOEXIC BACTERIA 

 NOT DESIGNED TO REl'LACE EFFICIENT MEANS OF FILTRATION 

 ALREADY IN USE. 



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

 genic bacteria, such as tj^phoid and choleia, is regarded as incidental 

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

 efficient means of preventing the appearance of these organisms in 

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

 the method as descril)ed is expected to replace or supersede slow sand 

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

 sometimes make it desirable to thoroughl}' sterilize a reservoir, and 

 under those circumstances the use of copper sulpliate 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 veiy great 

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

 some efficient method for destroying disease germs in water be emploj^ed 

 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 

 emplo}' copper sulphate with perfect safety in any municipal water 



