Voltaic Induction. 39 
other end, 6, so as to form a perfect metallic communication, through 
the coil, between the magnet and armature. From each of these 
portions of the instrument proceeds a conducting wire, c,d. The 
connections at a and 6 being preserved, if the armature be made to 
slide from the magnet, very brilliant sparks appear between the latter, 
at the last point of contact; and the wires, d, if taken into the mouth 
at the time of separation, will communicate very unpleasant shocks, or 
if brought close together, furnish a small but vivid spark. Yet the 
current actually passing through these wires, scarcely admits of detec- 
tion, even by the galvanic multiplier. As, however, the effect varies 
with the magnetic intensity, length of coil, &c., the observation will be 
best sustained by an appeal to experiment. The magnet, coil, ar- 
mature, and galvanic multiplier being the same in all cases, the fol- 
lowing results were obtained. 
1. One half the coil, moved downwards between the poles, gave, 
alone, a declination of 12°. 
2. One half the coil, moved downwards between the poles, with 
the armature, gave, alone, a declination of 70°. 
3. One half the coil, moved downwards between the fale and 
arranged as in fig. 6, gave, alone, a declination of 5°. 
Here it will be seen that a current, equal to 70° when the arma- 
ture merely passes through the coil, becomes diminished to ;; by 
merely making the magnet form a part of the circuit, as shown in fig. 
6. That the armature contributes nothing to this effect is shown by 
the fact, that an equal reduction takes place when the end of the 
coil, a, is separated from the armature and made to touch the mag- 
net, so that upon breaking off the contact of the armature, this end 
also becomes removed. ‘The result, therefore, clearly depends upon 
breaking off the circulation in the magnet and throwing it suddenly into 
the wires c, d.—It is easy to perceive why this arrangement should 
furnish a smaller current than even the coil alone; since, up to the 
period when the armature leaves the magnet, a close circuit exists 
and the wires c, d, cannot possibly receive any portion. After this 
separation the coil alone acts, but as its position is then necessarily 
lower down than when it is used alone, so the resultant current must 
be less. What then produces the shock, by this arrangement, when 
the wires c d are taken into the mouth, or the spark, when they are 
close to each other? ‘The galvanometer shows that there is scarcely 
any fluid circulating through them at the time. The result of my 
observation upon the three positions, establishes the fact, that the 
