312 M. E. Kolilraiiseb's T/ieori/ of the 



iug to which, in the case of a galvanometer furnished with a 

 damper, the velocity C may be determined from the first elon- 

 gation X of the needle. The formula is 



C"" -zL arc tan r— 



For the same galvanometer the time of oscillation T of the 

 needle and the logarithmic decrement X are constant, and hence 

 also the magnitude of the disposable charge of the battery is 

 proportional to the first elongation x of the needle ; which elon- 

 gation, on account of its smalluess, may be regarded as propor- 

 tional to the number of parts of the scale read off by the tele- 

 scope. The observations were as follows. 



A battery having about three square feet of coating, in which 

 no residue existed, was charged, the sine-electrometer was intro- 

 duced, and at the moment when the latter gave the charge 2-673 

 according to its own arbitrary unit, the discharge through the 

 galvanometer was effected. The first elongation amounted to 

 44-0 parts of the scale. Between the charging and discharging 

 a minute and a half intervened, and the concealed residue col- 

 lected afterwards amounted to 0-14. The repetition of this 

 experiment gave for the first elongation, in a case where the 

 needle was not completely at rest, 43-8, and in a subsequent 

 case 44"1 parts of the scale. In both of these last-mentioned 

 cases the residue was not detennined. 



The highly charged battery now remained for fifty minutes 

 without being discharged, at the end of which time the sine- 

 electrometer showed the charge 2-673, and was then discharged. 



Three such experiments gave for the first elongation of the 

 needle 44-0, 44-1, and 44-1 parts of the scale. 



Thirdly, a strong charge was permitted to remain standing in 

 the battery for 210 minutes, was then considerably weakened in 

 order to bring the charge down to 2-6.73, and afterwards gave 

 44*0 parts of the scale for the first elongation. In a short time 

 a concealed residue of 0-754 made its appearance, and the mea- 

 surement of the remaining portion of the residue, which, accord- 

 ing to estimation, would have given about twice the quantity, 

 was interrupted, inasmuch as the experiment was sufficiently 

 decisive. As therefore the concealed residue appeared to exert 

 no influence whatever, it was not at all taken into account in the 

 following experiments. Another battery was taken, and the 

 action of its discharge under different circumstances ascertained. 

 In the first column of the following little table are contained the 

 deflections (f> of the needle of the sine-electrometer; in the 

 second the square root of the sine of this angle, which from the 

 nature of the instrument is pi-oportional to the charge, but in 



