244 Intelligence and Miscellaneous Articles. 



these circumstances produces any marked effect is, however, amply- 

 proved by the numbers which follow, which, though given only as 

 first approximations, are within the limits of difference of the results 

 given (from galvanometric determinations) by former experimenters. 



As the polarization in most cases diminishes with very great rapi- 

 dity from the instant of breaking contact with the decomposing 

 battery, and as (for this and other reasons) the mode of measurement 

 by the first swing of the index-needle of the electrometer is not de- 

 serving of much confidence, it was necessary to devise a process by 

 which the electrometer could be charged at leisure up to any desired 

 potential, and then, for an instant only, placed in connexion with 

 the electrodes. The apparatus I employed bears a certain analogy 

 to the Wippe of Poggendorff, but differs from it in some essential 

 particulars, both of construction and mode of working. 



In a plate of vulcanite, or other good insulator, ten holes are cut 

 as below, and filled with mercury. Those marked E are connected 



with pairs of opposite quadrants of the electrometer, P with the 

 electrodes, B x with the decomposing battery, and B 2 with the auxi- 

 liary (or charging) battery. Also metallic connexion, as indicated 

 in the sketch, is permanently established between the two central 

 holes and the holes connected with the electrometer. 



The rocker consists of four wires, supported on an insulating bar 

 of vulcanite, the two outermost having three points, the middle one 

 longer than the others, and the two inner being similar, but wanting 

 one of the extremities. When the four middle stems dip vertically 

 into the four central mercury-cups, the other stems do not reach the 

 mercury in any of the other six cups. If the instrument be inclined 

 to the right the four prongs enter the holes to the right, thus simul- 

 taneously connecting the electrodes with the decomposing battery, 

 and the electrometer with the charging battery. When the instrument 

 inclines to the left, the electrodes are shunted from the decomposing 

 battery on to the electrometer, the latter having just before, by the 

 same action, been cut off from the charging battery, and thus left 

 charged. 



The modus operandi is simply this : — Leave the rocker leaning to 

 the right by its own gravity, decomposition and polarization going 

 on ; adjust the wires B 2 to different points in a wet string (or a nar- 

 row canal of water) closing the circuit of the charging battery; 



