THE SMITHSONIAN INSTITUTION. 377 



Is tlie induced current arising from a single clement, though it 

 produces in the human body such powerful shocks^ any more consider- 

 able? 



§ 32. Galvanic polarization. — A piece of wire of the length of 2, 3, 

 4, opposes to tlie galvanic current a resistance 2, 3, 4 ; the electro- 

 motive foi'ce of the battery and its resistance being known, the strength 

 of current can be computed from Ohm's law for any wire inserted. 

 Denote by E the electro-motile force of the battery, by IX the resist- 

 ance of the batter}', then if 7- denotes the resistance of the closing con- 

 ductor, the strengLh of current is 



and if a wire of equal thickness, but n times as long as the closing 

 wire, be used, the strength of current is 



Ji -'(- n r 

 This is rot the case with the insertion of liquids. Denote by E 

 and R the same ps above, and by io the resistance of the liquid in a 

 voltameter, which is inserted in the circuity then 



would be the strength of current, if Ohm's law applied here as to the 

 metallic wires. By separating the plates of the voltameter n times as 

 far apart, the strength of the current must be 



R -|- n vj 



If the strength of the current has been determined for a certain dis- 

 tance of the voltameter phites, it will be found for double, treble, or 

 four times that distance of the pohir plates — greater than should have 

 been expected from the immediate use of Ohm's formula. 



This .^ay be seen from a series of experiment-s made by Lenz, and 

 which were communicated, in volume XLIV of Poggendorff's An- 

 nalen, p. 349. Without going further into the description of the 

 method of observation employed by Lenz, i.. will suffice here to pre- 

 sent some of the results obtained. 



Wii.h metallic closing in his battery, (the current being magneto- 

 electric,) Lenz obtained a strength of currer t = 0.648, (according to 

 an arbitrary urit.) When the carrent passed through a concentrated 

 solution of sulphate of copper, ii whicli two copper plates were im- 

 mersed as electrodes, the force of current was fourd 



0.425, 

 •where the electrodes were 12.6 millimetres apart. Denoting the 

 whole resistance which the current had to overcome in the first case, 

 by 1, we have 



y = E = 0.648. 



