86 A. M. Mayer—liffects of Magnetization 
tions of this kind it gave no indications of polarity. But on 
lacing the rod in the helix, it of course was again magnetized, 
a feebly, by the earth’s induction. This fact serves to de- 
termine the distance at which the magnet, which determined 
the residual polarity, had to be suspended above the rod. 
this magnet is placed too near the rod, an interaction between 
it and the soft iron of the rod takes place by the inductive ac- 
tion of the magnet, and the vibrations of the latter are more 
frequent than when it is alone acted on by the earth; but if it 
be removed to a certain distance above the rod, then the magnet 
ism of the rod acts as a “damper” on the magnet, and its vibra- 
tions are slower than when it is only under the earth’s influ- 
ence. ere is, therefore, an intermediate position at which 
the magnet vibrates the same, whether the rod remains under it 
or is taken away. This distance, of course, varies with the rod 
used, but on an average it was about 3 inches. 
Thus arranged, the rod was allowed to remain until its tem- 
perature had become constant, and the scale reading in the tele- 
scope was stationary. 
The interpolar connections with the battery were made s0 
that the helix, on closing the circuit, would magnetize the rod 
with the same direction of polarity it already had from the 
earth’s action. The current was now passed from the 25 cells 
by plunging the amalgamated wire of the open part of the cit- 
cuit into a cup of mercury; then the scale-reading was imme 
diately noted; the circuit was at once broken, and another 
the three to six subsequent hours the room was entered, an 
readings of scale and thermometer obtained. 
. e well to give here a general account of the phe 
nomena which the rods exhibit when the voltaic circuit 
successively closed and opened. When the rod has, for the 
