Chemistry. 423 
eous body of any kind, or in any state of rarefaction or condensation, 
affords the slightest trace of being affected by magnetic forces. Gases 
may therefore be considered as occupying the neutral point in the mag- 
netic scale, intermediate between magnetic and diamagnetic bodies. 
The magnetic properties of compound bodies depend on those of 
their elements; and the bodies are rendered either magnetic or dia- 
magnetic according to the predominance of one or other of these con- 
ditions among their constituent parts. Thus iron is found to retain its 
magnetic power when it has entered into combination with other bodies 
of the diamagnetic class; the two forces acting in opposition to one an- 
other, and the resulting effect being only that due to the difference in 
their power. Hence the oxides and’ the salts of iron are still in a cer- 
tain degree magnetic, and the latter even when they are held in solu- 
tion by water; but the water may be present in such a proportion as 
that neither shall prevail; and the solution, as far as respects its mag- 
netic properties, will then be exactly neutralized. . These saline solu- 
tions, prepared of various degrees of strength, also afford a convenient 
method of comparing the relative degrees of force, both magnetic and 
diamagnetic, of different bodies, whether solid or fluid, but more espe- 
cially the latter, as they admit of the body under examination being 
suspended in another liquid, when its position of equilibrium will indi- 
cate which of the two substances has the strongest magnetic power. 
_ In one respect, indeed, the diamagnetic action presents a remarkable 
contrast with the magnetic; and the difference is not merely one of de- 
gree, but of kind. The magnetism of iron and other magnetics is 
characterized by polarity ; that of diamagnetics is devoid of any trace 
of polarity ; the particles of two bodies of the latter class, when jointly 
under the influence of the magnetic forces, manifest towards each oth- 
er no action whatever, either of attraction or repulsion. It has long 
been known that the magnetism of iron is impaired by heat; and it has 
been generally believed that a certain degree of heat destroys it en- 
tirely. The author finds, however, that this opinion is not correct; for 
he shows that, by applying more powerful tests than those which ha 
been formerly confided in, iron, nickel and cobalt, however high their 
temperature may be raised, still retain. a certain amount of magnetic 
power, of the same character as that which they ordinarily possess. 
From the different temperatures at which the magnetic metals appear 
to lose their peculiar power, it had formerly been surmised by the au- 
thor, that all the metals would probably be found to possess the same 
character of magnetism, if their temperature could be lowered suffi- 
ciently ; but the results of the present investigation have convinced 
him that this is not the case, for bismuth, tin, dve. are in a condition ve- 
ry different from that of heated iron, nickel or ‘cobalt. 
