762 Sir Oliver Lodge on 



nodes might even be short-circuited without altering the 

 frequency of vibration. 



(13) A tuned or resonant circuit can be maintained in 

 vibration with very little power, the only expenditure of 

 energy being that concerned with the dissipation term RC 2 , 

 together with a similar expression for the energy radiated 

 away which in the case of an open circuit may become 

 important. 



In some cases wave radiation is the thing desired, and in 

 that case the expenditure in this way is useful dissipation, 

 and the greater its proportional amount the higher the 

 efficiency of the arrangement. 



(14) That in an alternating dynamo, consisting of a rotor 

 and a stator, so far as mutual action is concerned it does not 

 matter which is which ; we are only concerned with the 

 relative motion between the two, and each can react on the 

 other by mutual induction. 



Putting all these simple principles together, and providing 

 both the rotor and the stator with as many tuned branch 

 circuits as are required, Dr. Goldschmidt has designed his 

 dynamo, whereby by mutual action and reaction between 

 stator and rotor the frequency mounts to a level such 

 that unavoidable hysteresis and other iron losses make 

 further additions to it uneconomical or impracticable. 

 And the highest frequency can be used for emission of 

 waves. 



In a machine which now exists at Slough, the revolutions 

 being about 4000 a minute, the frequency»attained directly 

 by multiple poles and high speed rotation is 12,000 per 

 second ; and this by action and reaction is multiplied by 4 ; 

 thus emitting a wave from the aerial 6J kilometres or about 

 4 miles long. 



A skeleton diagram of Dr. Goldschmidt's ingenious arrange- 

 ment can be given thus : without any statement that those 

 precise arrangements are necessarily adhered to. The rotor 

 connexions are supposed to be made with slip rings as usual : 

 the whole rotor, and whole stator, being of course connected 

 up, and not a portion only as in the diagram. 



An explanation is hardly necessary, since each branch 

 circuit is labelled with the frequency-constant to which it is 

 attuned/ and nodes are plainly provided for the attachment 



