670 



The phenomenon that occurred now was the following: when e.g. 

 in the 3'^' state h was charged to -|- 26 V, after ha\ing tirst been 

 brouf>-lit to -f- 28 V, we did not once more observe a deviation which 

 amounted to somewhat more than that for the change of the 

 potential value of b from -f- 30 V to +28 V (since the sensibility 

 at smallei' angle increases), but a passed over so great an angle that 

 the whole scale disappeared from the field, and a assumed almost a 

 position parallel to b: the needle turned suddenly. In state 4 this 

 phenomenon occurred immediately at the first potential decrease of 

 b with 2 V, and the same applies to the 5''' and 6'^' states, 

 whereas in contradistinction with this the first state exhibited stable 

 states throughout the scale for definite potential values of b. 

 The experiment seemed tiierefore to point to the existence of an 

 unstable state of equilibrium of a, which gradually shifted to an 

 increasing angle with b as the state of charge became more sensitive. 

 To ascertain, whether this displacement was a gradual one, the 

 turning point was approximated as nearly as possible for every state 

 separately; this was done by diminishing b in poteutial value not 

 by 2 Volts every time, but only by parts of 1 Volt. The result of 

 this was that, as had been expected, the 2"^ and 3''^ states were 

 still realisable throughout the tcale, the 4''', b^^\ B''» states on the 

 othej' hand only partially, but again in such a way that the said unstable 

 state of equilibrium, hence the turning point, occurred at a greater 

 angle, as the state of charge was more sensitive. 



When after the turning a had reached its new state of equilibrium, 

 it was not possible to make a return to its position through a slight 

 potential increase of b, which, considered in itself, would give rise 

 to a state of charge with a stable equilibrium outside the region of 

 turning. This too pointed to the existence of an unstable equilibrium. 



The explanation of the existence of such an unstable equilibrium 

 at the point of turning seems to me the following: 



In what precedes the change was already discussed of the 

 induced charge on b, in consequence of an angular displacement 

 of a; we saw how this change takes place for a definite angular 

 displacement to a greater degree, the greater the potential difference 

 is between a aud b, and the smaller the angle is between the needles. 



Taking this into consideration we may ask what will take place 

 when e.g. the state (+ 83, -f- 30, -|- 26,) V is realized, and when 

 the negative charge is continually supplied to b. 



In this the ratio of useful to injurious capacity will namely con- 

 tinually change for the before-mentioned reasons; it will become 

 continually greater; at a definite p,ngle the influence of this injurious 



