434 Strained Material, Ley den Jars, and Voltameters. [May 27, 



These equations, as has been seen, give with considerable accuracy 

 the actual value of the current flowing into the voltameter at any 

 moment during the greater period of the charging in the different 

 cases. The difference between the curves of charge in the different 

 cases is partly due to the different state of the distilled water and the 

 platinums, and partly to the level of the mercury on which the water 

 rested being slightly different in the different cases. To remove the 

 possibility of this latter cause of variation in the curves, the construc- 

 tion of the voltameter was altered, so that the level of the mercury 

 under the water was always so far away from the bottom of the plati- 

 num spirals, that any slight alteration in the level did not at all affect 

 the curve of charging, or discharging. We refrain, however, in this 

 preliminary note from giving any of the ' reductions of the curves we 

 have experimentally obtained with this improved form of voltameter. 



We may remark that the methods usually taken for measuring the 

 resistance of liquids are quite misleading if there is any analogy be- 

 tween voltameters and condensers with solid dielectrics. For instance, 

 on our assumption, the constant terms in the above expressions for u, 

 measuring, as they do, the current after a great time has elapsed, 

 really represent the ratio of the electromotive force of the battery to 

 the total resistance of the voltameter and connexions, and therefore 

 their reciprocals are measures of the several resistances. We need 

 hardly mention that in ordinary experiments the current is measured 

 for as short a time as possible, " to avoid polarisation, as it is said." 

 For small values of the time the current flowing into a volta- 

 meter, or liquid condenser, is very great, and in our opinion may be 

 regarded as nearly infinitely great ; for the first rapid rush of elec- 

 tricity is due to charging the voltameter as a condenser is charged ; 

 and if this rush is not quite instantaneous, it is because the electro- 

 motive force charging the voltameter does not immediately reach its 

 constant value. But just as the potential of the end of a cable sud- 

 denly attached to a battery will acquire its maximum value more and 

 more rapidly as the resistance of the battery and connexions is made 

 less and less, so by making the resistance of our single element used 

 to charge the voltameter less and less, and by measuring the time 

 integral of the current flowing in for shorter and shorter periods of time, 

 that is, by using galvanometer needles of more and more quickness of 

 vibration, a better and better approximation to the static capacity of a 

 voltameter is arrived at. And we found that when we had reduced 

 the resistance of our single cell to 0*04 of an ohm, by using in this 

 single cell a zinc plate having 15 square feet in area, the more and 

 more carefully we made the experiments, the more and more nearly 

 did the first discharge of a voltameter, which is always less than the 

 first charge, become equal to it. If the charge and discharge in volta- 

 meters do not prove to be as nearly equal as in glass Leyden jars, it 



