692 



1. the value of tlie force of the torsion, consequently the thickness 

 and nature of the suspension wire; 



2. the state of ciiarge in which we can distinguish high and low 

 states of charge, meaning that the potential a — h can be large or 

 small thus e.g. the state (a -f 30 Volt, /> Volt, c— 8 Volt) is a 

 higher state of charge than (a-f 12 Volt, /> Volt, c— 4 Volt). 



The meaning of condition 1 is sufTiciently clear in itself; as 

 regaids 2, if, with a definite wire one will always tiy to realise 

 higher states of charge, in the end the equilibrium from being 

 stable will always become unstable. For with a highei- state of 

 charge, the density of the lines of force between a and b and of 

 course also those between a and c (for there is a greater potential 

 difference between a and <• at the same time) will always be greater; 

 then also the electric cou|)le that occurs will increase in consequence 

 of a supposed slight displacement of the needle, so that the torsion 

 couple with a sufficiently high state of charge will finally be 

 unable to compensate this electric couple any more. Of course the 

 stable conditions are used for measurements ; yet it is practically 

 possible to approximate the unstable equilibrium with torsion, in 

 which case interesting phenomena occur; if e.g. under otherwise 

 equal conditions one increases the slate of charge continually, it 

 will in the end be impossible to give a fixed position to the needle 

 in or near the equilibrium (untwisted); seemingly the needle is at 

 rest, yet it gradually approaches the lower needle, at first with 

 slight velocity, but steadily increasing so Ihat the image of the scale 

 will shortly disappear from the field of the telescope; the parallel 

 position of the needles is almost reached. Such conditions are meant 

 in communication I, when we say that the needle "turns". 



As the behaviour of the electrometer has been accounted for in 

 the various states of charge, there still remains to examine the 

 behaviour in the various states of measurement where we shall also 

 be able to observe the importance of the "Labilisierungsprinzip". 

 To the conception of capacity, which is connected with it, I should 

 like to give the meaning of what Pulgar and Wulff *) call the 

 "total" capacity of the conductor, which conception is used by them 

 for cases similar to those considered here and for which the con- 

 ception of capacity, as Maxwell gives it, is not sufficient; for the 

 conductors a and c are not at Volt, nor does the angle of the 

 needles remain constant. 



Further 1 wish to distinguish between (cf. communication 1 p. 29) : 

 1 : useful, and 2 : injurious capacity ; meaning by useful capacity that 



I) J. DEL Pulgar and Th. Wulff. Ann. d. Phys. MO, p. 700, 1909. 



