THE SYDNEY HARBOUR COLLIERY. 137 



A nest of five boilers of the Lancashire type, 30ft. long b;y 

 8ft. in diameter, designed for a working pressure of 1201bs. per 

 square inch, are seated in brickwork. Provision is made for in- 

 creasing the number to 15, and a chamber has been built for a 

 Green's economiser of 832 pipes. The reservoir for boiler water 

 holds 80,000 gallons, and is built up of concrete. 



The feed water is pumped by Evans compound pump in 

 duplicate, the steam cylinders of which are 8Jin. and 12in., 

 and the rams Sin. in diameter; both rams and pistons having 

 a 9in. stroke. The brick stack has a total height of 192ft., and 

 forms a land-mark from the Harbour. The square base is 42ft. 

 high, the upper portion is circular in cross section, and has 

 an inside diameter at the top of 8ft. 2in. It is surmounted by 

 four lightning conductors, and two tapes leading from them 

 are grounded in the tank at its base. 



When sinking, six sump holes were put in at an angle, 

 so as to give lifting power to the shots, then while the broken 

 rock was being sent to the surface from the sump or advanced 

 hole formed, eight side holes were drilled vertically in the 

 bench left round the circumference of the shaft. Eack-a-rock 

 was the explosive used down to 650ft., after which gelignite 

 was employed. The shots were fired from the surface by 

 Nobel's low-tension electric exploder of the rack-bar type. The 

 record sinking w T as 82ft. for the fortnight. As the rock had a 

 tendency to flake off on exposure to the air, it was necessary to 

 put in a temporary wooden lining till they were ready to build 

 the permanent brick one. Curbs of Gin. by 5in. hardwood, 

 made in 12 segments bolted together, were used at first, set 

 6ft. apart from centre to centre; behind these were Gin. by lin. 

 hardwood backing deals. Each curb was hung from the one 

 above by hanging deals and was further supported by iron 

 dowels let into the rock at regular intervals. Twelve hard- 

 wood punch props of Sin. by 3in. section were also set between 

 the curbs, one to each segment. .Later QB-, the wooden curbs 

 gave place to rings of iron 3in. deep by fin. thick which were 

 suspended from each other by iron rods 4ft. Gin. long, with 

 hooks at either end bent in opposite directions. The iron seg- 

 ments were bolted together, one end being slightlv bent so as 

 to allow the straight end of the adjoining segment to fit into it. 

 The backing deals were wedged against the walls by wooden 

 wedges 9in. long, 6in. wide, and 2in. thick at their upper 

 end. The brickwork was built up in sections of 100 to 150ft., 

 according to the nature of the ground, and was started 25 to 

 50ft. above the bottom of the shaft, so that it should not be 

 damaged by blasting. Walling curbs of ironbark or tallow- 

 wood, 12in. wide and 4 Jin. thick, were used for each section 

 of walling. These walling curbs are made up of 12 segments 

 which butt together, and are bolted to a cod-piece placed over 



