THE SYDNEY HARBOUR COLLIERY. 



143 



thick; the segments weigh 18 to 19cwt. each. As the lower 

 end of the bottom ring rests against the rib cast on the top of 

 the bottom wedging curb, it has no flange cast on it. For a 

 similar reason there is no flange on the upper end of the top 

 ring. The space between the tubbing and the rock is packed 

 with pieces of wood and spear wedges. The holding down or 

 capping curb is cast flat on the top, and has a recess for the 

 top ring below. This is wedged in position in a similar manner 

 to the bottom curb, the rock being shorn back sufficiently to 

 enable the men to get at their Avork. Bricks are now built 

 up on the top of the holding-down curb. When the tubbing 

 is properly wedged, the plug holes, which till now have been 

 left open so as to relieve the pressure of water at the back, 

 are stopped by driving wooden plugs into them. 



While sinking, the top of the shaft was protected bv a 

 door that closed down flat over it. This door had rails fastened 

 to it, so that a trolly could be run underneath to receive the 

 body of a skip, or a skip itself could be raised from below 

 ;md lowered on the rails to be taken to the Tip. The door was in 

 two parts, and is opened by a worm and worm wheel worked 



- C. rtL i Ert pint 



SmaJl 

 Pnun 



*| 



|f 



Fig. 77. Signal Cord. 



by means of a hand winch. (Fig. 76). The arrangement by 

 means of which the signal cord is balanced and gradually let 

 out as sinking proceeds is shown in (Fig. 77). 



The head frame of the Jubilee shaft is made of ironbark 

 timber. The sticks fit into cast-iron shoes, to which they are 

 bolted, the shoes in turn being bolted to concrete pillars 

 (Fig. 78). To prevent water from entering the shoes and rot- 

 ting the wood, pitch was placed inside the casting, and the 

 timber when stepped forced out the excess of pitch, then the 

 space was caulked with tow. 



