172 EXPERIMENT STATION. [Jan. 



Tlie number of bacteria per cubic centimeter showed a 

 decided falling off after the treatment, but subsequently an 

 increase was noticed, although the number did not equal that 

 present before treatment. The first bacterial examination of 

 the water occurred one and two hours respectively after treat- 

 ment, at which time there w^as noted considerable decrease 

 in the number of organisms. It seems hardly creditable, 

 however, that the coj)per could have been sufficiently diffused 

 in the pond to cause such a rapid decrease in the number of 

 the bacteria in so short a time. Some Anabsena were present 

 in the pond previous to treatment, but none was observed 

 directly afterwards; neither were any Spirogyra noted either 

 before or after treatment. On the other hand, there were 

 various forms of life, such as Daphnia, etc., present, both 

 before and after treatment. Xo chemical analyses of the 

 water were attempted, since the ordinary methods of analysis 

 are not especially valuable in detecting slight traces of copper 

 in water. It would appear from the culture of seedlings in 

 glass vessels containing water and sand in which copper is 

 present, and from the results of chemical analyses of the 

 mud in the bottom of the reservoir, that a large amount of 

 copper is taken up by this mud. The results of copper treat- 

 ment of the pond in 1905 and 1906 show that the bacteria 

 never regained their former numbers. 



In a pond like this one, which is more or less polluted from 

 cesspools, one would naturally infer that bacteria would in- 

 crease rapidly after a few days. During August the pond 

 was in an even worse condition than in June, as a large num- 

 ber of dead fish, termed " suckers," which had died from some 

 unknown cause, were floating on the surface. Again during 

 October there was a fairly luxuriant growth of Anabsena 

 present for a few days, but this disappeared quickly, presum- 

 ably on account of the rather cold nights which occurred at 

 that time. 



At the time the treatment was under way, parallel labora- 

 tory tests were made. For this purpose we employed 18 

 liters of water from the college pond in two rectangular jars, 

 there being 9 liters in each jar, one of which was treated with 

 copper sulfate at the rate of 1 part of the sulfate to -4,000,000 



