ZIG ZAG COLLIERY. 119 



of the motor piston is smaller than that of the pump piston. 

 The controlling valves of the motor cylinder are made of lig- 

 num vitae, as this wood is sufficiently lubricated by the water. 

 The pump will work without the auxiliary or jockey valve, 

 but in that case must move faster. The auxiliary valve makes 

 a dead centre almost an impossibility, so with it the pump can 

 work very slowly so slowly that it can scarcely be seen to 

 move. 



Oakey Park Colliery. 



This colliery belongs to the Oakey Park Coal Mining and 

 Coke Company Limited, and has been managed by Mr. Robert 

 Hay for about sixteen years. The coal' seam is reached by 

 means of two shafts. The downcast is used for hoisting both 

 men and coal, while the upcast is used solely for ventilation 

 purposes, the ventilation being carried out by means of a fur- 

 nace with side fines, and exhaust steam from the pumping 

 engine. Eventually a fan will be installed, and the upcast shaft 

 will be used for travelling purposes, so as to increase the hoist- 

 ing capacity of the downcast shaft. The shafts are circular in 

 cross-section, and are bricked up near the top, but lower down 

 the natural rock stands fairly well, though no doubt it would 

 save trouble in the future if the shaft had been lined originally 

 from top to bottom. Wooden buntons are let into the sides to 

 support the guides, and a heavy oblong frame of wood is placed 

 on the top of the brickwork to support the superstructure. 

 The cage only carries one skip at a time, the full skip pushing 

 the empty one out at the bottom when changing, and vice 

 versa at the top. The cages are provided with safety catches 

 of the serrated cam type ; levers from the cam axles are con- 

 nected by chains to the draw-bar of the cage, by which means 

 the cams are kept off the guides. A spring attached to eacli 

 cam draws them together when the draw-bar is released. The 

 cages have shoes both on ends and sides. The end guides are 

 used when travelling through the shaft, for, being arranged 

 on the narrower sides, the cage has less play than if the cages 

 were guided from the longer sides, as is usual; but as these 

 end guides would be in the way of caging and uncaging the 

 skips, provision has to be made for changing to side guides 

 near the top and bottom of the shaft. About five feet below 

 the collar of the shaft side guides are fixed, and are continued 

 up the head frame. The ends of both end and side guides, 

 where the shoes first engage them, are bevelled off, so that the 

 shoes can embrace them easily, and as the cage slows down 

 at the end of a trip, there is no difficulty in changing from one 

 pair of guides to the other. The axles of the safety catches, 

 which are arranged for the end guides, pick up a light iron 

 sliding gate as the cage reaches the surface, and on descend- 

 ing leaves it behind to protect the mouth of the shaft. 



