694 



considered by itself. When, liowever, tlirongh this influence a definite 

 addition of charge causes a smaller rise in potential than would be 

 the case without it. this in itself means that the capacity of b -\- d 

 has been increased by it. It is this increase of capacity that is of 

 great advantage to the sensibility of charge in the system, and that 

 because this increase of capacity means increase of the useful capacity 

 of J, -\- d. Let us first imagine the phenomenon in two phases to take 

 place the one after the other (practically they act at the same time). 



I. the positive increased charge is distributed over b -\- d: the 

 upper needle describes the corresponding angle. 



11 the negative induced charge which is set free by this move- 

 ment near b spreads over A -\- d. 



The effect of I and 11 l(»gelher then comes to the same, as if I 

 had oidy taken place, but at the same time a greater part of the 

 added charge goes to those places of b, where the induced charge 

 of case II was to be set free. In my opinion it is clearly shown 

 in this way that the inflnence of phase 11 really consists in an in- 

 crease of the useful capacity of A. In the state of chai-ge (-f 14,0, — 6) 

 that usefnl capacity is yet more increased by the movement than 

 in the state of charge (+8,0,-4); from which follows that in 

 that slate the sensibility of charge will also be greater, because, as 

 was already said in Communication I, the sensibility of charge will 

 of course be all the greater according as a greater part of the added 

 charge causes a change in the lines of force between ^/ and /^ which 

 is attended by motion. Ultimately thei-e are limits to the nse of an 

 ever inci-easing state of charge; wMien e.g. the case of unstability as 

 described above, sets in. An approximation as closely as possible to 

 this unstable equilibrium is of course the most favourable condition 

 for the sensibility, because then (see above) the motion of the needle 

 will chiefly be the consequence of displaced induced charge and for 

 a small part only of the increase of chai-ge itself. 



The "Labilisierungsprinzip'" also occurs in some other electro- 

 meters, a. 0. in those of Wulff, Wilson (Kipsystem), whereas the 

 electrometer of Hoffmann aims at such a favourable variation of 

 the hinant-electrometer that the mentioned system was introduced 

 into the system for that very reason, for which purpose tlie shape 

 of the needle was chosen in a particular way. Yet the conception 

 that the "Labilisierungsprinzip" in itself would guarantee the greatest 

 possible sensibility in a system, is not correct according to my 

 opinion; with the application of this principle the ratio of useful to 

 injurious capacity will also remain of the greatest importance. If 

 e.g. one just imagines that in the system b -\- d, d possesses a great 



