691 



time light was (hiown upon the fact that the advantage of the 

 system will) regard to this had been obtaiiied l)y the fact that the 

 lines of force which undergo a change by addition of charge to the 

 system, act especially on the one vertical side of the upper needle, 

 i. e. will especially cause a moving couide. Let it be added that, 

 the arrangement once having become such as to show an asymme- 

 trical character, there had been introduced into the system at the 

 same time the principle called by Hoffmann the"Labilisierungs-prinzip", 

 which, considered by itself will yield "under certain conditions'' a 

 decisive advantage in relation to the sensibility of the apparatus, as 

 will become clearer yet from the following considerations. 



For this it is necessary to account for the behaviour of the electro- 

 meter in the various states of charge, as these are realized before 

 the measurement takes place. Suppose that one of the states of 

 charge has been given to the apparatus, e.g. (7 -|- 12 "Volt, b Volt, 

 c — 4 Volt, wire untwisted, angle of needles 30° (cf. I). The equilibrium 

 then arising is shortly due to the following: in consequence of 

 charging rt to 12 Volt — if b and c are still supposed to be Volt 

 3^et — a greater density of lines of force arises between n and b 

 than between a and c, in consequence of a slightei' distance between 

 a — b in relation to that of a — c; on account of this a resulting 

 electric couple will act on a, which can be compensated, however, 

 by a second electric couple in an opposite direction, which takes 

 place in consequence of charging c to negative potential ( — 4 Volt); 

 for b acts as a screen to the lines of force a — c (cf. also I pp. 24 

 and 25). If it is supposed that the needle has been suspended in 

 this condition 2('iVA(>?t/ torsion, then, in theory at least, the equilibrium 

 will continue; however, this is an unstable equilibrium, for with 

 constant potentials at a slight turning of the upper needle into the 

 direction that will decrease the angle with b, the density of the 

 lines of force between a and h will increase and a resulting electric 

 couple will arise according to the direction of the movement. The 

 equilibrium will also be unstable in the opposite direction, because 

 with an increase of the distance a — b, there will be a decrease in 

 the influence of b, and the influence of the negative of c will be 

 preponderating. The torsion of the suspension wire, however, can 

 yield a couple, if sufficiently large, which brings about a stable 

 equilibrium; the torsion, however, can have a value too, so much 

 so that it does not counterbalance these above mentioned electric 

 couples, in which case the equilibrium remains unstable. Given a 

 definite height and angle of needles there will exist two conditions 

 by which these cases are deteimined : 



