279 
1918.] The N.Z. Journal of Science and Technology. 
invariably of the slip-ring type, whilst the smaller are either slip-ring or 
squirrel-cage. 
Lighting .—In the Victoria mill it is the practice to use carbon-filament 
lamps in the battery and in places subject to vibration, as the life, com¬ 
pared with the metallic lamp, is considerably longer under these conditions. 
The current-consumption is, of course, much higher, but in the case of a 
cheap supply the lower cost of the carbon lamp more than counterbalances 
the power bill. It is. customary to hang these lamps on light springs with 
the object of damping the vibration, and this practice considerably increases 
the life of the lamp. In places not subject to vibration metallic-filament 
lamps of large candle-power are used, and have been found considerably 
cheaper in upkeep than arc lamps, and are preferable. The lighting is all 
direct current, and the voltage is 230. 
Refining .—In the Waihi Gold-mining Company’s plant the electrolytic 
method is used for refining the bullion. The slabs of bullion received from 
the melting department weight about 200 oz. and contain approximately 
12 per cent, gold and 87 per cent, silver. The stationary cathode type of 
cell is used, and each cell requires about 90 amperes at 3 to 4 volts. 
The following figures will be of interest as showing the amount of power 
used in a mill and the percentage consumed in the various departments 
of the mill. The figures are taken from the records of the Victoria mill 
of the Waihi Gold-mining Company (Limited). This mill is over twenty 
years old, and was not laid out with the intention of adopting the electric 
drive, consequently it cannot be considered to be so efficient (so far as the 
arrangement of the power plant is concerned) as a modern mill specially 
designed to be operated electrically. Moreover, the mill has been consider- 
ably extended from the original design, but at present 
to its full capacity. 
is not running up 
The actual consumption of current amounts to from 35 to 38 units per 
ton of ore crushed and treated, and the following table shows the percentage 
of power used in the various departments :— 
Crushers 
2-3 
Stamping 
26-2 
Tube mills 
33-2 
Treatment 
30-5 
Concentrates treatment 
3-2 
Lighting .. .. • 
3-9 
Workshops .. 
0-7 
> 
100-0 
The load on the mill is very constant, as shown by the fact that the 
daily load-factor averages about 95 per cent. The power of connected 
alternating-current motors is about 2,300 horse-power, and includes one 
300-horse-power and two 375-horse-power synchronous motors. The 
power-factor averages about 96 per cent. 
Conclusion. 
It will be seen from the above that electricity can be made to play a 
most important part in the gold-mining industry, and when intelligently 
used is the means of effecting a considerable saving. 
In a country like New Zealand, endowed with an abundant supply of 
water-power, capable in many instances of being harnessed at a reasonable 
