388 THE SCIENTIFIC PAPERS OF 



as in the case of coal-cutting machines in mines, tunnelling 

 machines, and machines in building, where water would be incon- 

 venient. One mode of transmitting hydraulic power had only been 

 partially alluded to in the paper, such as that which took place at 

 Schaff hausen, where turbines gave motion to quick-working pulleys, 

 on which steel ropes worked, transmitting power to a considerable 

 distance. 



Another mode in which such rotating power might be obtained, 

 and which was obtained more frequently perhaps on the Con- 

 tinent than in this country, was by sending the water through 

 high-pressure mains, and then making it work rotating hydraulic 

 engines, such engines generally working with oscillating cylinders ; 

 that, he thought, was a handy way of getting rotative power. 



He might also refer to another mode of transmitting power to a 

 distance, which, did not seem to have occurred to the author, 

 perhaps because it was of recent date, viz., by electric conductors. 

 If the dynamo-electric machine were employed for the production of 

 intense currents, such currents could be used for giving motion to 

 electrical engines for precipitating metals and for producing light. 

 The latter application was of practical interest, as it had actually 

 been employed for the illumination of lighthouses, as well as for 

 electric lamps armed with reflectors, so as to enable public works, 

 such as bridges, to be carried on during the night, and for lighting 

 large buildings. One or two facts might be interesting with regard 

 to that mode of transmission. A 4-HP. engine would produce per 

 hour a light equal to 1,000 candles ; therefore 100 HP. exerted in 

 that way would produce a light equal to 25,000 candles, or to 

 1,250 Argand burners, which would be equal to 25,000 cubic feet 

 of gas burned per hour, representing a value, at 4s. Qd. per thousand, 

 of 5 12s. Gd. The 100 HP. converted into an electric current 

 could be conveyed through a copper rod 2 inches in diameter, and 

 say a mile long ; such a rod would give a resistance of only about 

 { electrical unit, which would not in any way impede the electric 

 power. Therefore the power could be transmitted to a distance of 

 1 mile by means of such a rod of copper, and give there an aggre- 

 gate amount of light equal to 25,000 cubic feet of gas. He thought 

 that the method was of sufficient interest to be added to the other 

 modes of transmission, especially as it was gradually coming into 

 use. 



