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Supposed Polarity of Diamagnetic Bodies. 193 
e machine continued to work. But the deflection was not the 
greatest for the most diamagnetic substances, as bismuth, or anti- 
mony, or phosphorus; on the contrary, I have not been able to 
-assure myself, up to this time, that these three bodies can pro- 
duce any effect. Thus far the effect has been proportionate to 
the conducting power of the substance for Beppe Gold, sil- 
ver and copper have produced large deflec pee a and tin less. 
Platina very little. Bismuth and shane’ no 
2 ence there was every reason to believe that the effects 
were produced by the currents induced in the mass of the move — + 
ing metals, and not by any polarity of their particles. I proceeded 3 
therefore to test this idea by different conditions of the cores and, 
the apparatus. : 
2657. In the first place, if produced by induced.currents, the 
great proportion of these would exist in the part of the core near 
to the dominant magnet, and but little in the more distant parts ; 
whereas in a substance like iron, the polarity which the: whole 
assumes makes length a more important element. L.therefore ~ 
shortened the core of copper from 54 inches (2643.) to 2 itches, » 
and found the effect not sensibly diminished ; even when 1 inch ~ 
long it was little less than before. On the contrary, when a fine” 
iron wire, 54 inches in length, was used as core, its effects were, 
_ Strong ; when the length was reduced to 2 inches, t hey were, ° 
greatly diminished ; and again, with’a length of 1 ings ey fixe 
ther greatly re educed. It is not difficult to construct a, 
per, with a fine iron wire in its axis, so that when -- cers . (x 
tain length it should produce the effects of iron, and beneath that « - 
length the effects of co pper: ee Ria 
2658. In the next place, if: Feffect were proditced by Ni ed’ 
currents in the mass (2642.), division of the mass would® “Sto a 
these currents and so alter the effect; whereas if produced by: a. 
true diamagnetic polarity, division of the mass would BER 
the polarity seriously, or in its essential nature (2480.). 
: le. 
Copper filings. were therefore digested for a few days in dilute sul’ a x 
me acid.to remove BBY, adhering i iron, 2 n well ¥ 
an 
ned and stirred in. the air, ‘antil it was is 
t filrt sc 
is prepared by ae : 
é, three-quarters of 7 
as 28", 
