438 KANSAS CITY REVIEW OF SCIENCE. 



of the precious metals contained in the sulphur ores, being the most easily precip- 

 itated, are thrown down first in the tfnetallic state at the cathode, under the action 

 of a moderate current, and consequently the electrolytic bath is regenerated with- 

 out ceasing. There is merely one further operation, that of separating afterwards 

 those of the metals which have been thrown down together at the cathode. But 

 this final separation requires very little electric force, because this mass of metals, 

 already previously reduced to the metallic state and purified, when they are placed 

 together in another electrolytic bath and are dissolved there under the action of 

 the electric current, regenerate the thermic force or thermic work necessary for 

 the ulterior precipitation of each metal separately, saving the slight unimpottanl 

 and inevitable losses of thermic or electric action. 



We extract first the sulphur of carbon disulphide used, with or without pres- 

 sure. Carbon disulphide dissolves and removes promptly that part of the mixed 

 sulphur which is combined neither with silica nor iron. 



On re-distilling the decanted carbon disulphide loaded with dissolved sul- 

 phur, the latter is deposited in a state of purity. 



If the electrolysed ore is a multiple sulphide, containing especially much 

 iron we obtain then at the first operation sulphur and iron oxide. If m place of 

 then separating these two bodies by one of the methods descsibed above, we 

 electrolyse them feebly a second time in a bath composed e.g., of dilute sulphuric 

 acid, we obtain then pure sulphur at the anode, and iron as a basic sulphate at 

 the cathode. But sulphate of iron is in regular demand and of great use in in- 

 dustry. We may otherwise electrolyse it again or use it as an electrolytic salt for 

 the extraction of iron. 



In separating the mixture of sulphur and iron oxide there is no outlay of 

 work or of thermic power. On the contrary, in this operation there is produc- 

 tion of heat, and consequently of work. 



Practically, one and a half horse-power is required to produce electrolytical- 

 ly in one hour one kilogramme of copper set free from a sulphuretted copper ore, 

 a wonderful result in point of economy. — Les Monies. 



PHYSICS. 



TELEGRAPHING WITHOUT WIRES. 



At the British Association meetings at Southampton, Mr. W. H. Preece, 

 electrician at the General Post Office, ^dverted, in a paper on "Telephones," to 

 an experiment he had made of telegraphing from the mainland to the Isle of 

 Wight without employing a cable across the intervening space of water. This he 

 accomplished by utilizing the property of electricity named induction. The effi- 

 ciency of the telephone is frequently interfered with by currents of electricity 



