NORTH BULLI COLLIERY. 175 



divided into inches and decimals of an inch, the lines passing 

 across the whole width of each tube. The whole scale is 

 capable of being slid up and down to facilitate adjustment. 



An electric three-throw pump is used, having a capacity 

 of 4000 gallons per hour. 



The electric plant consists of a generator of 340 amp. and 

 250 volts, with no load, and 280 volts with full load. It 

 is used for coal cutters, pumping and lighting. This was the 

 first colliery on the South Coast to apply electricity to coal- 

 cutting machines. The generator is driven by a Fleming 

 side-crank engine, made by the Harrisburg Foundry and 

 Machine Works, Pennsylvania, Signalling is done by elec- 

 tricity generated by 10 Leclanche cells, and conveyed along 

 10 S.W.G. galvanised-iron wires. 



. Fig. 108 Hornsby Upright Wia'ter Tube Boiler. 



The boiler plant consists of a Hornsby and Sons tubular 

 boiler, and a colonial multitubular boiler at the mine ; there is 

 also a Hornsby boiler at the coke works. The Hornsby is an up- 

 right water-tube boiler. (Fig. 108.) The tubes are assembled 

 in nests ; those nearest the fire-box being inclined, while those 

 at the rear are vertical. A drum for holding 1 water and steam 

 is arranged at the top. The flame and hot gases from the 

 fuel act directly on the tubes ; the heating surface is large, and 

 as the heat acts on small quantities of water in one place, 

 steam can be raised rapidly. The constant rising of steam 

 from the internal surface of the tubes creates a powerful 

 circulation through the boiler, and tends to retard the deposi- 



