1880.] Strained Material, Ley den Jars, aad Voltameters. 429 



which from the following table, it will be seen accurately represents the 

 charging current from t equal 7 to t equal 25. After the current had 

 flowed into the voltameter for 1 hour and 7\ minutes, the cell was re- 

 moved, and the voltameter discharged through the galvanometer, the 

 connexions of which were simultaneously reversed, so that the dis- 

 charge deflection might be on the same side as the charge deflection, 

 and therefore less swinging about of the needle produced at the moment 

 of discharge. In the second of the following tables u is the discharge 

 current at a time t from the commencement of the discharge, and u' is 

 calculated from the equation 



?/ = 30'90e- 0-0553 ', 



which accurately represents the discharge current from t equal 5 to t 

 equal 25. The two exponents in the solutions of the differential equation 

 for the current flowing in during charge, and the current flowing out 

 during discharge, are 



—0-06245* and -0'0553£, 



which, considering that the resistance of the galvanometer, battery, 

 and connexions could not be neglected in comparison with that of the 

 voltameter itself, are remarkably nearly equal to one another, being 

 both — 0'06£ to two places of decimals. 



When it was desired to measure the time integral of the discharge 

 current during the first half swing of the galvanometer needle, rather 

 than the deflections, a short time after the commencement of the dis- 

 charge the galvanometer was short circuited for a sufficient length of 

 time before the Minotto's cell was removed for the needle to come to 

 rest at zero. 



Charging with oue Minotto's Cell of a Voltameter containing Dis- 

 tilled Water well freed from Gas, and the Platinum Spirals heated 

 red hot in vacuo. 



August, 1876. 



Time in 



Observed 



u' calculated from 



Difference 



minutes. 



current u. 



the formula. 



(ti — u') . 



1-5 



200 



164-2 



35-8 



2 



187-4 



161-9 



25-5 



3 



1737 



157-3 



16-4 



4 



163-9 



153-1 



10-8 



5 



156-0 



148-9 



7-1 



6 



149-3 



145-1 



4-2 



7 



1435 



141-6 



1-9 



8 



138-8 



138-2 



0-6 



9 



134-9 



136-0 



-1-1 



