Supposed Polarity of Diamagnetic Bodies: 199 
for iron. But the line a, b indicates those points for the commu- 
tator with which no eflect will be produced on the galvanometer 
by the induction of currents in the mass of the core. If the 
line be inclined in one direction, as 7, #, then these currents will 
produce a deflection at the galvanometer on one side; if it be in- 
clined in the other direction, as J, m, then the deflection will be 
_ on the other side. Therefore the effects of these induced curs 
rents may be either combined with, or opposed to, the effects of 
a polarity, whether it be magnetic or diamagnetic. 
2678. All the metals before mentioned (2655.), namely, gold, 
silver, copper, tin, lead, platina, antimony and bismuth, were sub- 
mitted to the power of the electro-magnet under the best adjust-_ 
ment (2675.) of the commutator. The effects were seouner 
than before, being now at a maximum, but in the same order; as 
regarded antimony and bismuth, they were very small, amount-  __» 
ing to not more than half a degree, and may very probably have, | * 
been due to a remainder of irregular action in some part of the * . 
apparatus.: All the experiments with the divided cores (2658, &c.) _. « 
were repeated with the same results as before. Phosphorus, stile *. 
phur and gutta percha did not, either in this o or in the former states, 
of the commutator, give any indication of effect at the sgalvane; , 
ometer. ‘ 
2679. As an illustration of the manner in which-this Spero hos 
of the commutator caused a separation of the effects of opper =. . 
and iron, I had prepared a copper cylinder core 2 inches i Tength — 
having an iron wire in its axis, and this being employed ifthe 2 
apparatus gave the pure effect of the Beonper with its induced cur-, = 
* 
. 
rents. Yet this core, as a Ww or © = 
dinary test-needle ; and when t Ula ge 
tor were not equidistant from the one s stop or the other (2670. **s 
2677.), the iron effect came out powerfully, overmuligg te former e 
and producing = srong contrary deflectionsa de: 'T 
_ platinum. core which I have used is an iiperoak pe er Binchesia’ 
“long and 0 62: of an inch thick: it points reap we 
the Poles of a,hor e electro-magnet-( a 
“but with the é 
or 
be m4 
Mich the bismuth, + # 
Shy & ducting power = 
f currents by induction in; 
| 0 f 
es its mass oom e effects were so minute and uncertain as 
s - to oblige me ay pi rimentally, it is without either po-. 
fore 
