96 
Description of Galvanometer. 
The Deprez and D’Arsonval Galvanometer consists of a 
rectangular coil of fine wire suspended between the poles of 
a strong horse-shoe magnet by an upper and a lower silver 
wire. The current to be observed is sent through these 
silver wires to the rectangular coil, which is defiected from 
its normal position, the plane of the magnet * 
Under proper conditions the galvanometer was found to 
be very delicate, and quite dead-beat, and therefore suitable 
for the investigation of currents of rapidly varying intensity, 
such as those considered below. 
To obtain the best results it was found : — 
(1) That the resistance between the terminals of the gal- 
vanometer must not exceed a certain limit This is necessary 
to maintain the dead-beat character of the instrument. The 
limit was about 90 ohms in the one used. As the resistance 
of the galvanometer was about 220 ohms, the resistance of 
the shunt was kept below 150 ohms. 
(2) That the coil must not suffer a violent or a long 
continued deflection in any one direction, otherwise the 
suspending wires take a temporary “ set ” from which they 
recover only after some time.‘|‘ 
The instrument was calibrated, and the defiection was 
found proportional to the current passing. 
Apparatus and Method of Experiments. 
In these experiments it was desired to notice : — 
(1) The variation of the current in a circuit containing 
an Eletrolytic cell in series with a battery. (This 
we shall call the Polarising Current.) 
(2) The variation of the current given by the polarised cell, 
the battery being out of circuit. (Depolarisation 
Current). 
* A full description of the galvanometer will be found in the Gomjptes Bendus 
94 , p. 1347 ( 1882 ). 
t This appears to point to the fact that the “ Elastic Eecovery ” of silver is 
slow. 
