352 



STUDIES ON FERMENTATION. 



increasing the power of the syphon by making the tube for 

 the escape of this gas longer than the other one.* 



It will be readily understood how, whether by this last 

 method, or by the diameter of the tubes, we may vary the 



Fig. 80. 



conditions of this circulation of air in the apparatus, on the 

 surface of the beer. 



* We may here remark that the system of gutters in the above 

 apparatus is much simpler than that described in connection with Figs. 

 76 and 77. The water which falls on the cover is carried oflF, when the 

 gutter is full, by a circle of grooves, inclined so that the streams running 

 from them meet and form more readily a sheet of water, which flows over 

 the exterior surface of the cvlindrical vessel. 



