702 



phase of tlie oscillations of the cjiinder is behind iliat of the current 



1)3' an amount v ; this follows from (9) and (13). Remembering 



further that in the deduction of (11) it has been assumed that 

 the circulating electrons are negative and that if they were positive 

 ones, the sign of B^ and the phase of the effect would be reversed 

 we are led to the following conclusion : 



Negative electrons. 



tu ^ ta„. The phase of tlie oscillations of the cylinder is a quarter 



of a period i)ehiiid that of the current. 

 to <^ ojj. It is a quarter of a period in advance. 

 M = w„. The vibration has the same phase as the current. 



Positive electrons. 



uj^oi„. The phase of the oscillations of the cylinder is a quarter 

 of a period in advance of that of the curi-ent. 



tu <^ iU(,. It is a quarter of a period behind that of the current. 



to = to„. The vibration of the cylinder and the current have opposite 

 phases. 



It is important to notice that there is a quarter of a period 

 difference of phase between the active couple i?, cos (at and the 

 current i:=Asui'.ot and likewise between the active couple and 

 the alternating magnetisation. This is always so, independently of 

 the relative values of to aud fo„ and of the sign of the circulating 

 electrons. 



§ 4. Short description of the apparatus. 



The alternating field which has been mentioned several times 

 already was excited by two coils placed with their axes along the 

 same vertical line and with a distance of about 1 cm between 

 them. They were mounted on a brass foot to which three foot screws 

 could give different inclinations. The coils were connected in series 

 and gave a field of about 50 Gauss. The iron cylinder was suspended 

 along their axis. This cylinder, 1.7 mm thick and in the first 

 experiments 7 cm long, was carefully turned of soft iron. Centrally 

 in its top there was bored a narrow hole of diameter 0.3 mm in 

 which a fitting glass wire was sealed. At its middle the cylinder 



