SOME NOTES 0\ TREATMENT OF SANDS FOR STOPE FILLING. 209 



reveal a desire on the part of those most interested in the direct- 

 ing of stope filUng- operations to interchange ideas and compare 

 results. It seems to the writer that this spirit of co-operation 

 would most fittingly find complete expression in the formation of 

 a commission composed of engineers, metallurgists and chemists 

 in touch with the subject. The commission, besides collecting 

 information, could have powers to arrange and carry on experi- 

 ments for the purpose of properly comparing existing proposals 

 and methods and trying new ones. Surely this would be the 

 quickest and in the long run the cheapest way of arriving at the 

 best working methods. 



ELECTRIC HOISTS ON THE TRANSVAAL MINES. 



The Electrician of January 6 contains a short description of elec- 

 trically driven hoisting and winding plant recently installed at 

 the Rand Collieries, near Johannesburg. At one of the Colliery 

 shafts two hoists have been fitted, one capable of lifting three 

 tons and the other six tons of rock. The conical drums, from lo 

 to i/i feet diameter, are coupled to direct-current separately 

 excited motors, working on the Ward-Leonard system. It is 

 estimated that one shilling per ton will be saved on the working 

 costs by the use of electrical winding. The power is supplied, at 

 10,000 volts, from the \'ictoria Falls Power Co., and is con- 

 verted at a transformer house to 6,000 volts. The six ton hoist 

 is at present the largest on the Rand. Elsewhere on the Johan- 

 nesburg mines much electrification is being carried on, mainly 

 by German firms. The Ward-Leonard system is principally used 

 for hoisting work, and the induction motor is supplied witTi high 

 tension current direct, and fitted with rheostatic control. 



THE EARTH'S REPULSIVE FORCE— Prof. C. D. 



Perrine, of the Cordoba University, Argentine Reoublic, com- 

 municates to the Monthly Notices of the Royal Astronotnical 

 Society a short note on photographic observations of Halley's 

 comet during its recent apparition, in the course of wh~ich he 

 remarks : " I notice the suggestion of Innes that the Earth may 

 have the power of repelling cometary tail-matter in a similar way 

 to the Sun. It seems to me doubtful if this is the case. If this 

 force is in reality light pressure, as seems very probable, the 

 small intensity of the sunlight reflected by the Earth could hardly 

 overbalance its gravitational force. If the force of repulsion is 

 electric or of some other nature, then the case is otherwise. 



