84 SMALL WATER SUPPLIES. 



thus altering the amount of stroke. A hand-wheel 

 is provided for the purpose of adjusting the stroke, 

 which can be done gradually, thus enabling any 

 desired quantity or pressure to be obtained. 



The main casting is entirely of gun-metal, fitted 

 with three gun-metal plungers working through 

 gun-metal packed glands directly in the valve cham- 

 bers. Each plunger is fitted with a substantial 

 gun-metal tail-rod, working through a gun-metal 

 stuffing-box in the valve cover. The crank shaft is 

 of steel, running in gun-metal adjustable bearings ; the 

 connecting rods of gun-metal coupled to the plungers 

 with large ball and socket joints. Efficient lubricat- 

 ing arrangements are provided, and large wearing 

 surfaces. 



Another advantage of these pumps is that they 

 work equally well when the shaft is vertical or 

 horizontal. This latter position allows a great deal 

 of latitude in erection, and is a condition which may 

 save expense, as will be pointed out when motor 

 power for driving pumps is considered. 



In most cases of estate water supply, it will gen- 

 erally happen that the quantities of water to be raised 

 are comparatively small, and the height to which it 

 is pumped fairly great. Under these circumstances, 

 then, the pumps which have been described will be 

 generally found to satisfy most conditions, and pumps 

 of any other kind, of a more or less fancy nature, are 

 generally to be avoided. When, however, it occurs 

 that a large quantity of water has to be raised to a 

 very moderate height, say 20 ft. or so, there is an 

 entirely different machine for the purpose known as 

 the centrifugal pump. It is a rotary pump, and pos- 



