212 JAMES CLERK MAXWELL 



which fall on it agrees with that of the waves which 

 it can itself emit, the oscillations which are set up in 

 the wire will be stronger than under other conditions, 

 the sparks seen will be more brilliant.* Hertz's re- 

 sonator was a circle of wire thirty-five centimetres in 

 radius, the period for such a resonator would, he 

 calculated, he the same as that of his vibrator. 



There is, however, very considerable difficulty in 

 determining the period of an electric oscillator from its 

 dimensions, and the value obtained from calculation 

 for that of Hertz's radiator is not very trustworthy. 

 The complete period is, however, comparable with two 

 one hundredth millionths of a second; in his original 

 papers, Hertz, through an error, gave a valuo greater 

 than this. '-'i 



With these arrangements. Hertz was able to detect 

 the presence of electrical radiation at considerable 

 distances from the radiator; he was also able to 

 measure its wave length. In the case of sound waves 

 the existence of nodes and loops formed under proper 

 conditions is well 'known. When waves are directly 

 reflected from a flat surface, interference takes place 

 between the incident and reflected waves, stationary 

 vibrations are set up, and nodes and loops places, that 

 is, of minimum and of maximum motion respectively 

 are formed. The position of these nodes and loops 

 can be determined by the aid of suitable apparatus, 

 and it can be shewn that the distance between two 

 consecutive nodes is half the wave length. 



&mo of tho ruisriuoncrH f thin uleetfU-ttl rraonuH-i- hav 

 l.rvn very fttrikinirlv hhown hy Pr.tVs><r Oliver 1* !.:. AVr Aii/wr, 

 February 20th, 1*00. , 



