478 DOROTHY F. PETTIBONE, F. B. BOGART AND P. F. CLARK 



lates the flow so that regardless of pressure changes, the height 

 of the jet will remain constant. 



But why retain a vertical column of water when it is obviously 

 the upward direction of flow which more than any other factor 

 renders the bubble fountain unsafe? A fountain (see fig. 1) was 

 constructed with a simple tube, having no crevices or complica- 

 tions placed at an angle of about 55 degrees from the vertical.^ 









'\ 1 V t 



Fig. 1. Simple Type of Fountain Which Should Be Generally Adopted. 

 No Contaminating Organisms Are Retained in the Jet or Water 



Even with a minimal stream flowing from this type of fountain, 

 the introduced organisms were all immediately washed away and 

 never did we find a single B. prodigiosus colony even on the plates 

 poured immediately after the introduction of the organisms. 



This simple type of fountain with an adequate collar guard to 

 prevent possible contact with the orifice would, we believe, solve 

 the problem and furnish water uncontaminated by human lij>s 

 even to a constant succession of thirsty persons. 



s Later experiments have shown that a tube erected at an angle of 15 degrees 

 from the vertical is adequate to prevent organisms from "dancing" on the 

 column of water. This makes the construction of a safe bubble fountain much 

 more practicable. 



