

THK WALLAHAH COLLIERY. 



251 



and tension of spring are so adjusted that the centrifugal 

 force increases faster than the tension of the spring, then the 

 engine will speed up under load. In this condition the engine 

 is liable to race, and it is to prevent racing that the dash-pot 

 is used. It is thus possible to adjust any engine so that it 

 will run faster under load than when running light, and still 

 regulate perfectly and with no tendency to race. On the other 

 hand the governor may be adjusted to run slower under load 

 than with no load. Perfect stability is obtained by the use 

 of dash-pots ; at the same time they increase the ease with 



Fig. 159. Wallarah Switchboard. 



which adjustments can be made. No difficulty is experienced 

 in adjusting these engines to govern within a limit of one 

 revolution, and the instantaneous variation of speed when the 

 entire load is thrown on or off is seldom more than one 

 per cent., while the action of the governor is unusually quick, 

 the engine returning to its standard speed within the space of 

 two seconds. 



The new electric plant was supplied by Siemen Bros., and 

 consists of a direct current compound field generator, of 200 

 kw., 0-6TO amp., 42T-425 rev., and 270-300 volts. It is driven 

 by a "VV. H. Allen, Son and Co. vertical compound engine with 

 13^ and 21in. diameter cylinders and 9in. stroke. It has 425 



