86 SMALL WATER SUPPLIES. 



air, and this will rarely be found on estates installed 

 for a particular and separate purpose. The method 

 about to be discussed is known as the " air lift " pump. 

 In principle and operation it is very simple. Air is 

 injected by means of a nozzle placed below the work- 

 ing water level, and rising, carries up water along 

 with 'it. The submerged parts are subject to no 

 wear whatsoever, and except for corrosion, are prac- 

 tically indestructible, even when working in gritty 

 water which is often fatal to deep well pump pistons. 

 The air compresser and receiver, which are the only 

 parts requiring attention, are, of course, at surface 

 level. The Worthington Pump Co., who make air 

 lift pumps, record the fact that the air lift pump has 

 the advantage of increasing the yield of any deep 

 well ; whether this is the case or not with every well, 

 the air certainly imparts sparkle and life to the water, 

 which is certainly desirable. Of course an air com- 

 presser has to be erected and driven by some form 

 of motive power. Some years ago an air compresser 

 was a cumbersome and expensive piece of apparatus, 

 but there are now on the market some good machines 

 of small size which run at a high speed, such as those 

 manufactured by Messrs. Alley Maclelan, of 

 Glasgow ; Messrs. Reavel & Co., of Ipswich ; The 

 Worthington Pump Co., London. Where electricity 

 is handy, an electrically driven air lift pipe may 

 prove its advantage above other forms, but like all 

 engineering questions each case has to be considered 

 on its merits, and a knowledge of ascertaining these 

 merits is not a subject which a writer can describe, 

 but is the monopolized possession of the engineer 

 possessing experience and common-sense. In cases 



