28 METHOD OF DESTROYING ALG^J IN WATER SUPPLIES. 



The decrease in the number of organisms as the result of this treat- 

 ment during the next twenty-four hours was very decided. In two 

 days the surface was clear and the water had lost its blue-green color, 

 becoming brown, due to the dead organisms held in suspension. 

 There was a slight increase in odor during the first two days after 

 treatment, but this was followed by a gradual subsidence until it had 

 entirely disappeared, not to appear again that season. The following 

 list of counts made from surface examinations at one station illus- 

 trates what went on throughout the reservoir, and shows the almost 

 immediate effect of a 1 to 4,000,000 solution of copper sulphate upon 

 the number of filaments of Anabdena flos-aquaa. The treatment was 

 made July 9. 



Filaments per 

 cubic centimeter. 



July 6 3, 400 



July 10 54 



July 11 8 



July 13 



July 15 



July 20 



It remains to be seen what the condition will be during the coming 

 summer, but it is believed it can never be any worse than at the 

 time of treatment, and it is reasonable to suppose that there will be 

 considerably fewer organisms this } 7 ear than last. Even though an 

 annual treatment of the reservoir prove necessary, involving a cost of 

 from $25 to $50, the alreadj^ great improvement in the quality of the 

 water will certainly make it justifiable. 



Other experiments of a similar character were carried on in different 

 parts of the country with reservoirs of a capacity of from 10^000,000 

 to 600,000,000 gallons. While the results were all favorable, it is 

 deemed best not to publish any detailed account until the effect of the 

 treatment can be followed through another season. The summer of 

 1903 was cold and wet, and in some cases the decrease in the number of 

 organisms may have been due to these factors. However, the several 

 instances of the very sudden and rapid disappearance of forms which 

 were present in tremendous quantity, without any reappearance, 

 indicated that the treatment was most effective. Those in charge of 

 these water supplies reported that they were well satisfied with the 

 result. 



EFFECT OF COPPER, UPON PATHOGENIC BACTERIA. 



TYPHOID. 



The value of copper sulphate as an agent for the destruction of 

 algae polluting reservoirs suggests its use in cases where the organism 

 is pathogenic. Since this salt is fatal to the algal growths, it seemed 



