A24 Scientific Intelligence. 
The magnetic phenomena presented hy copper and a few other met- 
als are of a peculiar character, differing exceedingly from those exhib- 
ited by either iron or bismuth, in consequence of their being complica- 
ted with other agencies, arising from the gradual acquisition and loss of 
magnetic power by the iron core of the electro-magnet, the great con- 
ducting power of copper for electric currents, and its susceptibility of 
being acted upon by induced currents of magneto- -electricity, as descri- 
bed by the author in the first and second series of these researches. 
The resulting phenomena are to all appearance exceedingly singular 
and anomalous, and would seem to be explicable only on the principles 
referred to by the author. 
Pursuing his inductive inquiries with a view to discover the primary 
law of magnetic action from which the general phenomena result, the 
author noticed the modifications produced by different forms given to 
the bodies subjected to experiment. In order that these bodies may set 
either axially or equatorially, it is necessary that their section, with ref- 
erence’ to the plane of revolution, be of an elongated shape: when in 
the form of a cube or sphere, they have no disposition to turn in any 
direction: but the whole mass, if magnetic, is attracted towards either 
‘magnetic pole; if diamagnetic, is repelled from them. . Substances di- 
vided into minute fragments, or reduced to a fine powder, obey the 
same law as the aggregate masses, moving in lines which may be term- 
ed diamagnetic curves, in contradistinction to the ordinary magnetic 
curves, which they every where intersect at right angles. "These move- 
ments may be beautifully seen by sprinkling bismuth in very fine pow- 
der on paper, and moped on the paper while subjected to the action of 
a magnet. 
The whole of these facts, when carefully considered, are tedalvable; 
by induction, into the general and simple law, that while every particle 
of a magnetic body is attracted, every particle of a diamagnetic body 
is repelled, by either pole of a magnet. These forces continue to be 
exerted as long as the magnetic power is sustained, and immediately 
cease on the cessation of that power. Thus do these two modes of ac- 
tion stand in the same general antithetical relation to one another as 
the positive and negative conditions of electricity, the northern and 
southern polarities of ordinary magnetism, or the lines of electric and 
of magnetic force in magneto-electricity. Of these phenomena, the 
diamagnetic are the most important, from their extending largely, and 
in a new direction, that character of duality which the magnetic force 
was already known, in a certain degree, to possess. All matter, in- 
deed, appears to be subject to the magnetic force as universally as it is 
to the gravitating, the electric, the cohesive and the chemical forces. 
Small as the magnetic force appears to be in the limited field of our 
