200 



MICRO-ORGANISMS IN WATER 



Pulverised and Finely Sifted Sterilised CoTie 

 Temperature at which vessels were kept = 7°C. 



' In both cases after standing half an hour the water was clear. 



Dry, White, Finely Sifted, and Sterilised Sand 



Temperature at which vessels were kept = 7° C. 



^ After from three to seven minutes the sand had in both, cases fallen to the bottom. 



In the above experiments insoluble substances were 

 used exercising no chemical action either on the water 

 or on the bacteria ; in order to ascertain whether the 

 results of sedimentation would be influenced by more or 

 less soluble substances acting chemically on the water, 

 and doubtless also on the bacteria, Kriiger made the 

 following further investigations :^ 



Finely Sifted and Sterile Magnesiutn Oxide 

 Temperature at which vessels were kept = 7° 0. 



' The water became clear after standing between 20 and 30 hours. 



^ The water was rendered alkaline by the addition of the magnesium oxide. 



