ON THE POLARITY OF THE DIAMAGNETIC FORCE, 
243 
and scale before me, the experiments were completely under my own control. 
Finally, the course of the current through the helices was as follows: — Proceeding 
from the platinum pole of the battery it entered the box along the wire v), fig. 2, which 
passed through the bottom of the latter; thence through the helix to H', returning to 
E' ; thence to the second helix, returning to E, from which it passed along the wire 
to the zinc pole of the battery. A commutator was introduced in the circuit, so 
that the direction of the current thus indicated could be reversed at pleasure. 
EXPERIMENTS — DEPORTMENT OF DIAMAGNETIC BODIES. 
A pair of cylinders of chemically pure bismuth, 3 inches long and 0*7 of an inch 
in diameter, accompanied the instrument from Germany. These were first tested, 
commencing with a battery of one cell of Grove. Matters being as sketched in 
fig. 2, when the current circulated in the helices and the magnet had come to rest, 
the cross wire of the telescope cut the number 482 on the scale. Turning the wheel 
W' so as to bring the cylinders into the position fig. 1, the magnet moved promptly, 
and after some oscillations took up a new position of equilibrium ; the cross wire or 
the telescope then cut the figure 468 on the scale. Reversing the motion so as to 
place the cylinders again central, the former position 482 was assumed ; and on turn- 
ing further in the same direction, so as to place the cylinders as in fig. 3, the position 
of equilibrium of the magnet was at the number 493. Hence by bringing the two 
ends /rand o to bear upon the astatic magnet, the motion was from greater to smaller 
numbers, the position of rest being then fourteen divisions less than when the bars 
were central. By bringing the ends m and p to bear upon the magnet, the motion 
was from smaller to greater numbers, the position of rest being eleven divisions 
more than when the bars were central. 
As the positions here referred to will be the subject of frequent reference, for 
the sake of convenience I will call the position of the cylinders sketched in fig. 1, 
Position 1; that sketched in fig. 2, Position 2 ; and that sketched in fig. 3, Position 3, 
The results which we have just described, tabulated with reference to these terms, 
would then stand thus : — 
I. 
Bismuth cylinders, 
length 3 inches, 
diameter 0*7. 
Position 1. 468 
Position 2. 482 
Position 3. 493 
In changing therefore from position 1 to position 3, a deflection corresponding to 
twenty-five divisions of the scale was produced. 
