Intelligence and Miscellaneous Articles, 235 



the second interruption-place was struck. Thenceforth the move- 

 able plate of the condenser was insulated, and retained the charge it 

 had received. 



Its quantity and kind were then measured by an electrometer con- 

 structed on SirW. Thomson's principle, after removing the plates of 

 the condenser one from the other. 



The process which was thus submitted to observation is therefore 

 the series of electrical oscillations remaining, after the interruption 

 of the primary current, in the induced spiral connected with the 

 condenser. Since these oscillations proceed from one plate of the 

 condenser to the other in an unbroken conduction without any issue 

 of sparks, they pass much more regularly and are much more nume- 

 rous than those observed in the connecting arcs of Leyden batteries. 

 The length of my micrometer permitted the reading-off of 35 posi- 

 tive and the same number of negative phases when the distance 

 between the spirals was 34 centims. The time of an entire oscilla- 

 tion (positive and negative together) amounted to 2 ^ 1 of a second ; 

 the total duration of the 35 oscillations observed was therefore ^ of 

 a second; and when I was obliged to break off the observations, the 

 oscillations were still by no means so feeble that, with a greater play 

 of the micrometer, a long series of them could not have been 

 observed. 



The result of experiments in which I varied the distance of the 

 condenser-plates, and consequently the electric capacity of the con- 

 denser, was, that the duration of the oscillations was but very little 

 affected by the capacity of the condenser. I have, in a previous 

 communication*, pointed out that even a close- wound spiral itself 

 operates as a condenser, since the turns at one end become charged 

 positively, and those at the other end negatively, and are only sepa- 

 rated from the less strongly charged positive or negative layers in 

 their vicinity by the very thin insulating layers of silk; hence an 

 electric coating is accumulated on both sides of the insulating layer. 

 Since the lessening of the capacity of the condenser has so little in- 

 fluence on the duration of the oscillation, it follows that the conden- 

 satory capacity of the spiral must have considerably exceeded that of 

 the condenser. 



In order to discover the possible retardation of the distant effect, 

 it was necessary to discover a conspicuous point in the course of the 

 electric oscillations that could be very sharply determined. The first 

 moment of the commencement was unsuitable, since, apparently, the 

 current commences with a velocity rising from zero, and this only 

 gradually increases ; hence the strength of the current at first in- 

 creases, at the most, proportionally to the square of the time. The 

 reason of this is to be sought in the fact that the primary current 

 also, during the time of the spark, vanishes only gradually, and 

 hence the induced electromotive force in the secondary circuit is by 

 no means suddenly developed there in perfection, but itself first 



* Verhandlungen des naturh. med. Vereins zu Heidelberg, April 30, 1869. 

 In the earlier observations, with the aid of the current-testing leg of a 

 frog, I had verified as many as 45 oscillations, the total duration of which 



