1907.] 



PUBLIC DOCUMENT — No. 38. 



171 



to physiologists for many years; but the treatment of large 

 volumes of water with this chemical is, so far as we know, 

 comparatively recent. Those who wish to become familiar 

 with the more technical features of this subject are referred 

 to the older literature, much of which is in German, and to 

 the more recent publications of the United States Department 

 of Agriculture and our o^vn State Board of Health. 



The treatment given during 1906 was similar to that of 

 1905, and consisted in applying 1 part of copper sulfate to 

 4,000,000 of water. The copper sulfate was placed in a 

 coarse bag attached to a canoe, which followed concentric 

 circles over the pond until the copper sulfate was all dissolved. 

 Samples of water were taken daily for bacterial examination 

 a few days before treatment and each day after until July 

 19, when the experiment was discontinued. The usual bac- 

 terial methods were employed, with the following results : — 



Table shoiving the Jtesults of treating the College Pond with Copper 

 Sulfate at the Rate of 1 Part of Cox)per Sulfate to 4,000,000 

 of Water. {Treated June 14, 1906.) 



[Number of bacteria per c. c. of water.] 



June 10 7,0051 



11 6,0341 



12 5,7571 



13 7,1881 



14. 

 14, 



14, 

 15, 

 IG, 

 17, 

 18, 

 19, 

 20, 

 21, 



23, 

 24, 



25, 



7,1581 

 1302 

 5G3 

 1424 

 156 

 15G 

 341 

 554 

 769 

 1,000 

 1,000 

 756 

 768 

 927 



June 26, 



27, 



28, 



29, 



30, 



July 1, 



2» 



3, 



4, 



5, 



9, 

 11, 

 13, 

 15, 

 17, 

 19, 



1,085 

 1,231 

 1,265 

 1,006 

 1,365 

 1,231 

 1,308 

 1,231 

 1,006 

 1,084 

 1,000 

 1,208 

 1,208 

 1,275 

 1,462 

 1,770 



1 r.cforc treatment. 



2 One hour after treatment. 



3 Two hours after treatment. 



* Twenty -four hours after treatment. 



