116 Electric Lighting for Mines. 



The current it furnishes must not be of too high an electro- 

 motive force, for if any shock were felt on taking hold of any 

 bare wire there would be an aversion on the part of the 

 miners to handle or use any of the apparatus, whilst the 

 machines in use have been so arranged that the electro- 

 motive force will remain nearly constant, and thus maintain 

 to the same degree of brightness either one or its maximum 

 number of lights without altering the speed of the driving 

 engine. 



Too much care cannot be exercised in carrying out this 

 portion of the work, for it must be recollected that the 

 apparatus will be left in charge of those who probably know 

 nothing whatever of electrical matters, and who could not, 

 therefore, know where to look for or to rectify even the 

 slightest fault which might occur. But with properly con- 

 structed apparatus and a little training, no difficulty has 

 been experienced by the engine-drivers employed in the 

 mines in maintaining the dynamo machine in an efficient 

 condition. 



The surface and underground lights are kept on two cir- 

 cuits, and under the control of two switches. All the lights 

 are enclosed in outer globes of thick glass, the dirt and dust 

 about the places necessitating a covering for the lamps 

 which could be cleaned and handled roughly. In the 

 crushing-rooms flexible springs are used to suspend the 

 lanterns, it being found that the constant vibration to which 

 the lamp was subjected caused the carbon loops to occasion- 

 ally break off. 



Each lamp is controlled by a separate switch and a safety 

 cut-out, whilst a protecting wire guard is necessary in places 

 where the lamp is liable to be struck with quartz or imple- 

 ments. From the engine-house to the shaft overhead con- 

 ducting wires are used, not necessarily covered with insulating 

 material. These wires end in an iron junction-box, having a 

 main fusible cut-out. Down the shaft the current is lead 

 by an insulated cable constituting the leading wire, and 

 enclosed in a galvanised-iron pipe of suitable conductivity 

 which serves for the return lead. Copper strips soldered 

 over the joints of the pipes ensure an electrical connection. 

 At each plat an iron junction-box is provided, having a 

 safety cut-out leading to the branch wire for the cross-cuts 

 and levels. 



These branch wires are smaller but similar to the main, 

 being also enclosed in iron pipes, which serve as the return 



