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LXII. E. K. SCOTT. 
driven station the charges which are proposed by the London 
and District Hlectrical Supply Company may be cited; there 
is to be a yearly charge of £3 per kilowatt and a running 
charge of a farthing per unit, supplied so that if the customer 
uses full current for say a quarter of the total hours in the 
year or has what is called a 25% load factor, then he will 
pay at the rate of x‘«ths of a penny per unit. 
It should be noted that it is more important to have a 
high load factor for a water power plant than for a fuel 
power station, because a natural water flow is only con- 
trollable to a certain extent, whereas a fuel supply can be 
controlled to any degree. In practically all water power 
plants some water must run away uselessly, and the amount 
will vary according to the number of and the height of the 
peaks as compared with the steady all day load. It might 
be thought that the difficulty could be got over by electric 
storage, but hydro electric stations are unsuitable places 
for storage batteries and in any case there would be con- 
siderable loss of energy in changing from direct current to 
alternating. In several hydro electric plants situated on 
rivers, special water storage reservoirs are provided. At 
Zurich for example, water is delivered from the river to a 
reservoir by turbine pumps which run when the main gener- 
ators are not fully loaded. Then, when the power of the 
river gets low the reservoir can be drawn upon. 
Power House.—The power house and hydraulic works for 
a high head, such for example as Barron Falls, differs 
considerably from what would be required at the Trawool 
dam witha head of say 100 feet. The amount of water to be 
dealt with is very much smaller, and it would be brought 
to the power house through a steel pipeline of comparatively 
small cross-section, whereas at Trawool the power house 
would practically form part of the dam and the water be 
lead direct into a turbine chamber and away through a 
