Dr. 0. Lodge on Electric Radiation, 49 



S 

 Static capacity, — =25 centim. 



Self-induction, —=8320 „ 



Characteristic factor, log— =7"9. 

 a 



Rate of vibration, 10 million per second. 

 Wave-length, 29 metres. 

 Dissipation-resistance, 22,500 ohms. 

 Initial stock of energy, about 300,000 ergs. 

 Power of initial radiation, 128 horse-power. 

 Number of vibrations before energy would be at this rate 

 dissipated, about 3. 



The electrical surgings obtained while the Hertz oscillator 

 is working are of just the same character as are noticed when 

 a Leyden jar is discharging round an extensive circuit ; but 

 whereas from a closed circuit the intensity of the radiation 

 will vary as the inverse cube of the distance as soon as the 

 circuit subtends a small angle, the radiation from a linear or 

 axial oscillator varies in its equatorial plane only as the 

 inverse distance, as Hertz showed. 



Hence, for obtaining distant effects the linear oscillator is 

 vastly superior. Its emission of plane-polarized, instead of 

 circularly-polarized, radiation is also convenient. 



(I may mention that a thundercloud and earth joined by a 

 lightning-rod or by a disruptive path constitute a linear 

 oscillator ; and hence radiation-effects and induced surgings 

 may be expected to occur at very considerable distances from 

 a lightning-flash.) 



Exciting this oscillator by a very large induction-coil, 

 extraordinary surgings are experienced in all parts of the 

 building, and sparks can be drawn from any hotwater-pipe or 

 other long conductor, whether insulated or otherwise, and from 

 most of the gas-brackets and water-taps in the building, by 

 simply holding a penknife or other point close to them. From 

 conductors anywhere near the source of disturbance the 

 knuckle easily draws sparks. 



Out of doors some wire fencing gave off sparks, and an 

 iron-roofed shed experienced disturbances which were easily 

 detected when a telephone-terminal was joined to it, the other 

 terminal being lightly earthed. [Sometimes I utilized the 

 wire fencing as one of the plates of the oscillator, and thus 

 got still bigger and further spreading waves.] 



The waves thus excited are from 30 to 100 yards long, and 

 optical experiments with them would be as difficult and vague 

 as are experiments on sound-waves of corresponding length. 

 Small oscillators can, however, easily be employed which shall 



Phil. Mag. S. 5. Vol. 28. No. 170. July 1889. E 



