404 THE ADDRESSES, LECTURES, ETC., OF 



to a second, that to a third dynamo-machine, and this again has 

 given motion to the carriage upon the rails, which latter perform 

 the function of conducting wires. The same power has thus been 

 four times transmitted, showing the great facility with which we 

 can reconvert it again and again from mechanical into electrical, 

 and from electrical into mechanical, effect ; and alter its character 

 from a current of high potential to a current of low potential, or 

 vice versa. 



I will now allude to an application of electricity lately made by 

 Dr. John Hopkinson, which appears to me to be full of promise. 

 Mr. Nebel will set it to work. It is an electrical hoist. Imagine 

 this to be at the top of a warehouse, and the chain ten times as 

 long as it could be made in this instance, and you will observe 

 that by putting on the current of this dynamo-machine, the Aveight 

 (which might be much heavier), will be lifted readily, and may be 

 stopped and lowered at will according to the position of the brushes 

 upon the dynamo-commutator. 



Another application which has been made with great effect, is 

 that of raising the wire which is used in sounding by Sir William 

 Thomson's wire sounder. On board the " Faraday," the machine 

 has been employed, and the wire is drawn up in an extra- 

 ordinarily short space of time. "We find that by these means 

 we can make a sounding in 2500 fathoms in an hour, because we 

 can go on with the steamer while the electric machine is pulling 

 in the wire. The only drawback which was found in the early 

 trials was that, the machine having been placed near the com- 

 passes, the latter were influenced magnetically : the caution, 

 therefore, to be observed, is to put it in a part of the ship away 

 from the compasses. 



When losses by unnecessary wire-resistance, by Foucault currents 

 and by induced currents in the rotating armature, are avoided, 

 as much as 90 per cent., or even more, of the power communicated 

 to the machine is realised in the form of electric energy, and vice 

 versd the reconversion of electric into mechanical energy can 

 be accomplished with similarly small loss. Thus, by means of 

 two machines at a moderate distance apart, nearly 80 per cent, of 

 the power imparted to the one machine can be again yielded as 

 mechanical energy by the second, if we leave out of consideration 

 frictional losses, which latter need not be great, considering that a 



