1880.] Strained Material, Ley den Jars, and Voltameters. 417 



which we have obtained from the general solution (5) of the diffe- 

 rential equation by a method explained towards the commencement of 

 this paper. 



Charging of a Voltameter, consisting of Platinum Plates dipping in 

 ordinary Water, with one Minotto's Cell. 



February 14, 1878. 



Time in 



Observed value 



u f calculated 



Difference 



lluilLll tO ■ 







(it ' — w') . 



4 



. . . » 690 



587 , 



103 



10 



618 



537 



81 



20 



526 



'479 



. . 47 



30 



455 



431 



14 



40 



398 



390 



8 



50 



355 



356 



—1 



60 



322 



327 



— 5 



70 



. . . 297 



303 



—6 



80 



279 



283 



-4 



90 



265 



267 



-2 



100 



252 



253 



-1 



110 



240 



241 



-1 



120 



230 



231 



-1 



130 



223 



223 







140 



216 ... 



216 







150 



211 



210 . ... 



1 



160 



205 



205 







170 



201 



201 







180 



. .. 198 



198 







190 



195 



195 







After the deflection had diminished from 690 to 195 in rather more 

 than three hours, the Minotto's cell was suddenly removed, and the 

 voltameter discharged through the galvanometer, the terminals of 

 which at the same moment were reversed, so that the deflections for 

 discharge should be on the same side as those for charging, in order 

 to somewhat diminish the swinging of the needle. 



The general differential equation (1) when applied to the discharge 

 curve thus obtained by experiment, leads to the solution — 



?/ = ir4 + 158-5e-°-os79* ...... (7), 



from which u' given in the third column of the following table has 

 been calculated. 



