1889-90.] NATURAL HISTORY OF GROUND WATERS. 163 



Third experiment, less carbolic acid mixture taken, but concentrated 

 (2 litres). Taste of acid noticeable for several days after, but gave no 

 reaction with ferric chloride. Remained sterile four days, but not till the 

 twelfth day did germs appear in litres 500. 



Further experiments undertaken with artesian wells gave results com- 

 pletely in accord with above. 



Fraenkel notes here that the sterility of water might be due to the fact 

 that carbolic acid had sterilized a layer of soil at base of tube, which for 

 several days filtered away the organisms in ground water, but that finally 

 they penetrated this layer and then appeared in well. To overcome this 

 objection he caused the well, some days after the complete re-establish- 

 ment of the germs in it, to be thoroughly cleaned out by scrubbing it for 

 half an hour with a long-handled brush. Then water examined gave 

 the following result. — 



and the well remained sterile for the four following days. 



It was evident that germs originated from the sides of tube itself, 

 and not from ground water. Mechanical cleaning was sufficient to 

 remove them. 



He concludes therefore that except in certain cases (dependent upon 

 soil) the ground water may be looked upon as germ free. Conditions 

 w^hich might lead to an infection of ground water, are character of soil 

 above the water, layer rather loose in character ; water layer too close 

 to upper surface of ground, occurrence of drains in water layer which 

 were not perfectly tight, or finally, the presence of muddy wells. 



He finally studied the effects of the disinfection of artesian wells upon 

 spores of bacteria. He could not use anthrax spores from their danger- 

 ous nature, but used almost equally resistant hay bacillus spores, and 

 spores of blue milk bacillus, as well as the micrococcus prodigiosus. 



Results were all favorable ; sterilization was easy. He tried the dis- 

 infectant characters of lime, but found there was not sufficient amount of 

 water in artesian well to dissolve it, and danger of spoiling well by the 

 formation of a sort of mortar which could not be easily removed. 



He next started a series of experiments on two kettle wells, also situ- 

 ated in the court of the Hygienic Institute, and each containing about 

 r3 cubic metres of water. 



