THE WALLARAH COLLIERY. 247 



will not stop for repairs unless absolutely obliged to do so, 

 but say the machine will last their shift, and pass it on to the 

 next party in that condition. The following shift does likewise 

 if possible. The result is that the machines do inferior work, 

 and there is a tendency to wear the machine out quicker. 



Ventilation is carried out by means of a 16ft. Walker's 

 indestructible fan. This is driven by ropes from one of 

 Walker Bros., of Wigan, engines. A duplicate engine is ar- 

 ranged end on to the other, which is used when repairs have 

 to be undertaken. There used to be seven pumps driven by 

 Fetter petroleum engines, but now only two are in use. There 

 are also three small electric three throw pumps, used for dip 

 workings, and one Aldrich electric pump, made at Allentown, 

 U.S.A., also a steam pump, which will soon be replaced by a 



Fig. 155. Jeffrey Shortwall Coal Cutter. 



main electric pump. The vaporiser of the Fetter petroleum 

 engine is first heated by a simple form of paraffin blow lamp 

 for five to ten minutes, after which the oil tap is opened and 

 the fly-wheel turned by hand (Fig. 156). This causes the 

 piston to move forward, and at the same time draws in a 

 charge of air and oil through the upper valve. The piston 

 then returns and compresses the mixture into the back part of 

 the vaporiser, the oil having by this time become converted 

 into vapour or oil gas. The mixture explodes with the heat, 

 and drives the piston out with considerable force. At the 

 end of the outward stroke the lower valve commences to open 

 and the piston returns, expelling the burnt vapour through 

 the exhaust pipe. The oil flows through a copper pipe to the 

 governor valve. This valve controls the supply of oil to the 

 engine, permitting more or less to pass as the load on the 

 engine varies, and is so constructed, that if from any reason 

 the engine should stop or the governor band break, the oil 



