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HYDKAULICS AND ITS APPLICATIONS 



(4) Meters for waste detection. 



(5) Venturi meters. 



(1) This type suffers from the disadvantage that all the pressure head of 

 the supply is lost, and that when used for domestic supply it must there- 

 fore be placed at the top of the building. It is, however, well fitted for 

 the measurement of small flows. The " Parkinson " meter, which is of 

 this type, is illustrated in Fig. 350, and has given excellent results in 

 measuring the power water delivered by the City of London Hydraulic 

 Supply Company. In this case the meter is applied to measuring the 



Inlet 



Inlet 



Outlet Outlet 



FIG. 350." Parkinson's " Low Pressure Water Meter. 



exhaust water from the various machines. Here water from the inlet pipe 

 is maintained at a uniform level in the inlet chamber by means of a float 

 and valve V. This valve is constructed as shown so as to be balanced 

 whatever the pressure in the supply pipe. On leaving this chamber by 

 the pipe P, the water flows into the annular space S formed in the drum D. 

 This drum is hollow and contains four compartments formed by oblique 

 radiating plates E, which overlap each other to the extent of about 90. 

 Each compartment opens at its inner periphery into the space S, and in 

 turn receives a supply of water. The centre of gravity of the water in the 

 compartment being, on account of its position, to one side of the axis of 

 the drum, this produces a rotation about the axis and brings the next 

 compartment into communication with the space S. At the same 



