WU.I.IAM SIEMI-.XS, l-.R.S. 33! 



upon well crcosoted cross sleepers. At the Paris Electrical 

 Kxliibition the current was conveyed through two separate con- 

 ductors making sliding <r rolling contact with the carriage, 

 \vlicivas in [In; electric railway now in course of construction in 

 tin- north of Ireland (which when completed will have a length of 

 1 _ miles) a separate conductor will be provided by the side of the 

 railway, and the return circuit completed through the rails them- 

 selves, which in that case need not be insulated ; secondary 

 liaiti-ries will be used to store the surplus energy created in 

 running downhill, to be restored in ascending steep inclines, and 

 for passing roadways where the separate insulated conductor is 

 not practicable. The electric railway possesses great advantages 

 OUT horse or steam-power for towns, in tunnels, and in all cases 

 where natural sources of energy, such as waterfalls, are available ; 

 but it would not be reasonable to suppose that it will in its 

 present condition compete with steam propulsion upon ordinary 

 railways. The transmission of power by means of electric con- 

 ductors possesses the further advantage over other means of 

 transmission that, provided the resistance of the rails be not very 

 great, the power communicated to the locomotive reaches its 

 maximum when the motion is at its minimum that is, in com- 

 mencing to work, or when encountering an exceptional resistance 

 whereas the utmost economy is produced in the normal condi- 

 tion of working when the velocity of the power-absorbing nearly 

 equals that of the current-producing machine. 



The deposition of metals from their solutions is perhaps the 

 oldest of all useful applications of the electric current, but it is 

 only in very recent times that the dynamo current has been prac- 

 tically applied to the refining of copper and other metals, as now 

 practised at Birmingham and elsewhere, and upon an exceptionally 

 large scale at Ocker, in Germany, where the motive power is 

 derived from a water-wheel. The dynamo machine there employed 

 was exhibited at the Paris Electrical Exhibition by Dr. Werner 

 Siemens, its peculiar feature being that the conductors upon the 

 rotating armature consisted of solid bars of copper 30 mm. square, 

 in section, which were found only just sufficient to transmit the 

 large quantity of electricity of low tension necessary for this 

 operation. One such machine consuming 4-horse power deposits 

 about 300 kilogrammes of copper per 24 hours. 



