454 Production of Statical Electricity by Heat and Light. 



passing over a paraffin plate could appreciably electrify it. 

 For this purpose a cylindrical plate of paraffin was placed 

 under a similar piece of wood, the air space between the two 

 being about 1 mm. deep. In the middle of the wooden disk 

 was a hole which could be connected through a glass tube to 

 a water-suction pump. When the pump is in action a strong- 

 current of air is drawn over the surface of the paraffin, and 

 the current is similar to the one which might be induced by 

 the heating during exposure to sunshine. No charge what- 

 ever could be detected on the paraffin after this treatment. 



It has until now been generally held, that it is only through 

 friction and similar mechanical operations that a body may 

 acquire an electrical charge, but the thermo- and pyroelectric 

 properties of the so called hemimorphous crystals indicate 

 that the temperature of a body has an influence on its charge, 

 and the experiments described above show that radiant as 

 well as mechanical energy is able to produce electrostatic 

 charges on bodies exposed to its action. 



The actual amount of electrification is difficult to deter- 

 mine. Several experiments have given discordant results, 

 so that there must be some disturbing causes. 



Especially the action of internal friction seems very strong. 

 The electrification by friction has therefore been the subject 

 of my last investigation. 



The experiments made show, that when two pieces of 

 paraffin, which have the same temperature, were rubbed one 

 with the other, both pieces were negatively charged, but by 

 keeping the temperature of one piece of paraffin higher 

 than the temperature of the other, the warmer piece shows 

 after rubbing a positive charge and the colder a negative 

 charge. 



I have made other experiments of similar nature. A glass 

 rod, for instance, rubbed with a piece of woollen cloth was 

 positively charged, but if the same woollen cloth before 

 friction was made very hot the same glass rod showed after 



rubbing a negative charge. 



To explain these experiments I have taken some new 

 principles into account. 



I think the different bodies at the same temperature may 

 be in different electrical states. I call this state the "elec- 

 tron temperature" of the bodies, and I think. this temperature 

 is very different from the ordinary " molecular temperature." 

 By rubbing two bodies one with the other, the body which 

 has the lower electron temperature would be negatively 

 charged, and the body which has the higher electron tem- 

 perature would be positively charged. The rise of the 



