Aerator for Laboratory Aquaria. By J. F. Gemmill. 25 



D. Bottle, of e.g. IjOO com. capacity, with neck about 2 in. 

 wide, and a tight cork pierced with the necessary holes. 



E. Bent tube, of about § in. internal diameter, one end con- 

 nected with C, the other passing up within the wider tube F to 

 8 in. from the top, and opening there. 



F. Wider tube, 6 or 7 ft. high, and of about t 9 q in. internal 

 diameter, passing through the cork, and connected at the upper end 

 with M, the air-tube supplying the aquaria. 



H. A bent tube of about h in. internal measurement, and about 

 10 in. shorter than F, with an opening at the top of the bend. One 

 limb of the tube pierces the cork and reaches nearly to the bottom 

 of the bottle, while the other is led to a waste sink. 



M. Air-tube for supply of aquaria. 



When the tap is turned on, water mixed with air emerges at 

 the top of the bent tube E within the wider tube. The water is 

 free to fall down the wide tube into the bottle, while the air remains 

 higher up. Pressure rises inside the bottle and the tubes coming 

 from it, and the water used escapes by H, and thus runs to waste. 

 This gives a supply of air along M under as much pressure as the 

 height of H allows. If more air is supplied than is used for aera- 

 tion, it gradually displaces the water in D as far down as the lower 

 end of H, and then the surplus escapes. 



The opening at the top of the bend on H ensures against syphon 

 action taking place, and thus destroying the internal pressure. 

 Should the water pressure at the tap slacken and give a diminished 

 supply of air, the water level in the bottle and in the tube F rises 

 till it adjusts itself to the lessened internal pressure. Should inflow 

 at tap cease altogether, any water which may be in the tubes above 

 the level of B escapes by this opening, and accordingly it is as well 

 to have attached thereto a piece of rubber tubing leading to the 

 waste sink. 



The attachment between tap and aspirator needs to be secure. 

 The nozzle of the tap should be of suitable shape, and pressure 

 tubing, firmly tied on and strengthened by having string or a strip 

 of strong tape wound round it, should be employed. 



