98 



Popular Science Monthly 



AlH 



An air-compressor supplies air to a chamber surrounding the water-pipe in tlie well. The 

 air passes through small perforations into the water, producing bubbles which rise slowly 



Making Water Pump Itself 



DOES water seek its own level? 

 Yes, with an if — if the water is 

 the same density throughout. If 

 the density of water in two connecting 

 \cssels differs, tlie le\c'l of the lighter 

 water will he higher. 



There are different ways in whidi 

 density can be affected. One is by heat; 

 another is by adding to the water some- 

 thing that is lighter than itself — air, 

 for instance. This can be shown in a 

 very simple way with a tea-kettle and 

 a short tube. l'"il! liie keltic with water 

 and insert tlie tube in its spout until it 

 nearly touches the bottom of the spout, 

 riieii blow bul)i>ies into the spout 

 through the tube, '{"he bubbles will mix 

 with the water in the spout and lighten 



it. The solid water in the kettle will 

 then overbalance the lighter aerated 

 water in the spout ; the hea\ier water 

 in the kettle will force its wa\- into the 

 spout in an endeavor to establish 

 equilibrium, antl the spout will over- 

 flow. The water will continue to flow 

 from the spout until the water le\-el in 

 the kettle becomes so low that ecpiilib- 

 riuin is established. Then the llow 

 will cease. It is ai)|iarent that the force 

 of the air has little to do witii the action, 

 for the air is blowing ai^aiiist tlie direc- 

 tion of llow of the wati'r. Thi' water 

 really pumps itself. 



Ki'cping the c.ise of the ki'tlk' in 

 mind, we will now see how it suflicos to 

 illustrate the princi|)le of the air-lift. 



