Electric Lighting for Mines. 115 



great waste in the recovery of the gold during the process 

 of amalgamation. In the underground workings generally 

 the principal lights used are oil-lamps at the plats or entrance 

 to the drives, and candles in the crosscuts, levels, and backs. 

 As a rule, a mine has either too little or too much air — that 

 is to say, some of our mines are so badly ventilated that in 

 certain parts a candle will not burn, whilst in other mines 

 the draught of air is so great that it is difficult to keep the 

 candle alight, and under these circumstances about half the 

 candle is wasted by the grease running away. An examina- 

 tion of nearly all our mines shows at once that the arc-light 

 would be unsuitable for surface works and unworkable for 

 below ground, where there are few places large enough to 

 hang an arc-lamp. Most of our drives and levels are some 

 six or seven feet wide, about the same height, and varying 

 from two hundred to eight hundred feet in length; con- 

 sequently they require a number of small lights only. 

 Above ground arc-lights might be used, but as a number of 

 them would be required (all the places to be lighted being 

 detached), it would be an expensive method not only in its 

 first cost, but in its maintenance. It, therefore, became 

 obvious that the incandescent system of electric light would 

 prove the most suitable for all conditions and circumstances. 



In designing and carrying out an electric-light installation 

 at a mine, two or three points require careful consideration. 



Deriving an electric current from a dynamo machine, 

 which must be kept in motion during the whole time a light 

 is required, it was found necessary to provide a motor inde- 

 pendent of the mining plant. 



Where water-power is not available a small steam-engine, 

 of a good working type and sufficiently large enougli to do 

 the maximum amount of work required of it, must be pro- 

 vided. This auxiliary engine can, of course, be supplied 

 with steam from the regular boilers in use, thus involving no 

 extra outlay for firing. 



Little need be said about the engine — any kind or make 

 will answer, provided it be of an economical type with 

 respect to its steam supply ; but it was found an advantage 

 to fit on an extra fly-wheel to ensure its steadiness in running, 

 and special large lubricators to feed the oil for a length of 

 time without stopping the engine. The dynamo machine 

 used is of a special type. Running constantly both day 

 and night, its working parts require to be durable, the arma- 

 ture not too large and heavy, and the speed not too high. 



