
TRANSACTIONS OF THE SECTIONS. 9 
when the electro-magnet was in activity, between two drops of oil suspended in the 
midst of the ferruginous liquid, or between a piece of bismuth and one of these drops. 
I have therefore reason to doubt whether such movements, which have been con- 
sidered as proving the mutual action of diamagnetic bodies, are not rather owing to 
the movement of the entire liquid mass of which we have spoken. Although it is 
extremely probable that the mutual action of diamagnetic bodies does exist, and, 
according to the laws admitted also by yourself, still it must be allowed that this 
action is very feeble, and it is much to be desired that an experiment should be made 
by which it might be clearly demonstrated. 
I pass over in this extract, which is already too long, my experiments upon the 
different inductive power of various metals, on the time of induction in the different 
metals, &c. ; but I must finally call your attention to the part of these researches 
which I believe to be the most important, and which relates to an experimental 
theory of diamagnetic phenomena. 
A mass composed of very fine powder of perfectly pure silver or copper, the con- 
ductibility of which is destroyed by the interposition of a thin film of oil of tur- 
pentine, duly suspended in proximity of the polar surface, is repelled at the instant of 
the passage of the current, and continues to oscillate like a mass of bismuth. If one 
composes other similar suspended matter in which the quantity of metal and con- 
ductibility gradually increases, one sees the silver or copper pendulums first repelled 
from the pole, then come to a stop after a constantly decreasing number of oscilla- 
tions, until at last they present the phenomenon which you have called revulsion, 
due to the production of induced currents. In the same way a small copper 
or silver disc, fixed to the extremity of a straw lever suspended by a cocoon 
silk near to a pole, is repelled or attracted at the beginning or end of the current 
without being subject to any movement of oscillation: if this disc is cut so as ‘to 
destroy its continuity as much as possible, to prevent the development of the induc- 
tive. current, it then exhibits the phenomenon of oscillation like bismuth. These 
phznomena, and several others which you have described, and which it is unneces- 
sary to adduce here, have led you and Weber, with much reason, to admit the 
hypothesis of a diamagnetic polarity in reverse direction of that acquired by mag- 
netic bodies. I hasten to add, that my experiments do not lead me to reject this 
hypothesis, as you, and more recently M. Verdet, have done; and that, on the con- 
trary, it seems to me in conformity with physical analogy to admit that diamagnetic 
substances, when subjected to magnetic force, assume a polarity the same in kind 
as, but reverse in direction of, that acquired by iron, which polarity has a duration 
varying according to the nature and conductibility of the substance, and which, 
according to these circumstances, tends to transform itself into an inductive instanta- 
neous current. I abstain from entering here into a minute development of these theo- 
retical views, which every one can do for himself, and proceed at once to speak 
experimentally. It is perfectly true that you, and more recently M. Verdet, have 
demonstrated that the phenomenon discovered by Weber in bismuth can be explained 
by simply referring to the inductive currents, and without having recourse to dia- 
magnetic polarity ; but the same experiments have not proved the non-existence of 
diamagnetic polarity. In the first place, I recollect that oxide of copper is strongly 
magnetic ; consequently a mass of copper filings with oxidated superficies cannot, 
when it acts on the electro-magnet, develope inductive phenomena similar to those 
of bismuth or purecopper. Jn fact, I found with my inductive apparatus, which is 
certainly the most powerful and delicate hitherto constructed, that a mass of copper 
filings oxidated at the superficies, such as used in organic analysis, gives inductive 
currents as if it were a magnetic body. In order to prove by our experimental 
method that diamagnetic polarity does not exist, one must prove that no induced 
currents are obtained in the direction demanded by that supposed polarity, when one 
makes an electro-magnet act on a diamagnetic body, incapable of conducting in- 
duced currents, and in quantity sufficient to induce sensible effects on our apparatus. 
To show the superiority of my apparatus, I have only to mention, that a stratum of 
500 grammes of colcothar brought near, but not in contact with the electro-magnet, 
and consequently without any apparatus of rotation, produced an induced current of 
10° to 15° and more, according to the strength of the battery. With this same appa- 
