If W is the weight of iron present per c.c. at about io° C., then for ferric salts Io 6 K =266W-0'77 and for ferrous salts 10 6 K =206W - 077, the quantity - 0.77 arising from the diamagnetism of the water of solution.
To account for diamagnetism, Weber supposed that there exist within the molecules of diamagnetic substances certain channels around which an electric current can circulate without any resistance.
Ordinarily a substance composed of asymmetrical molecules is paramagnetic, but if the elementary magnets are so conditioned by their strength and concentration that mutual action between them is possible, then the substance is ferromagnetic. In all cases however it is the diamagnetic condition that is initially set up - even iron is diamagnetic - though the diamagnetism may be completely masked by the superposed paramagnetic or ferromagnetic condition.
Diamagnetism, in short, is an atomic phenomenon; paramagnetism and ferromagnetism are molecular phenomena.
The original memoirs themselves on radiant heat and on magnetism were collected and issued as two large volumes under the following titles: Diamagnetism and Magne-crystallic Action (1870); Contributions to Molecular Physics in the Domain of Radiant Heat (1872).
In 1841 he found that he required rest, and it was not till 1845 that he entered on his second great period of research, in which he discovered the effect of magnetism on polarized light, and the phenomena of diamagnetism.