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III. — An Automatic Aerating Apparatus, suitable for Aquaria, etc. 

 By James F. Gemmill, M.A. M.D. 



{Read December 15, 1909.) 



The Aerator (fig. 1) to be described costs little and is reliable, 

 besides having other advantages which are referred to later. The 

 essential features of the apparatus are: (1) a constant inflow of 

 water into a closed vessel forces the contained air under pressure 

 through the aerating nozzles ; (2) the vessel is emptied automatic- 

 ally at regular intervals by siphon action, air being allowed to 

 replace the water siphoned off. During this period, which is 

 relatively short, there is a pause in the output of air. 



Explanation of the lettering on the Sketch. 



A. Constant inflow of water under 8 feet or more of water 

 pressure. The inflow must be sufficient to insure the advent, at 

 the proper time, of siphon action. If too scanty the water will 

 simply trickle over the summit of the siphon tube. But the in- 

 flow should nob be so great as to compete effectively with the 

 emptying action of the siphon. In practice the proper rate can 



.be got in a few minutes by manipulating the water-tap, but most 

 water-taps require readjustment for the first few days. 



B. A small vessel (the water valve vessel) suspended within 

 the large vessel C. B is kept full by the inflow and it overflows 

 into C. The end of the tube F just dips into the water within B. 



C. A large glass bottle (e.g. of f gallon size) with moderately 

 wide mouth closed by a rubber bung with perforations for the 

 tubes A, D, E and F. The bung must be quite air-tight, and it 

 should be fixed securely in the neck of the bottle so that it may 

 not be driven out when the pressure rises within the bottle. The 

 constant inflow of water tends to fill the bottle, driving the con- 

 tained air up the aerating tube D. Sooner or later the bottle C is 

 emptied by the siphon E, and then the filling up process starts 

 anew. 



D. Aerating tube of T 7 g in. internal measurement. The lower 

 end just pierces the rubber bung and is bevelled, while the upper 

 end reaches above the summit of the siphon. From the upper end 

 a small indiarabber tube (K in the sketch) leads to the aerating 

 nozzles, the number of which may be multiplied indefinitely by 



