148 Royal Society. 



Thus it appears that different bodies are acted upon by the mag- 

 netic forces in two different and opposite modes ; and they may ac- 

 cordingly be arranged in two classes ; the one, of which iron is the 

 type, constituting those usually denominated magnetics ; the other, 

 of which bismuth may be taken as the type, obeying a contrary law, 

 and therefore coming under the generic appellation of diamagnetics. 

 The author has examined a vast variety of substances, both simple 

 and compound, and in a solid, liquid, or gaseous form, with a view 

 to ascertain their respective places and relative order with reference 

 to this classification. The number of simple bodies which belong 

 to the class of magnetics is extremely limited, consisting only of 

 iron, which possesses the magnetic property in an eminent degree, 

 nickel, cobalt, manganese, chromium, cerium, titanium, palladium, 

 platinum and osmium. All other bodies, when either solid or liquid, 

 are diamagnetic ; that is, obey the same law, with regard to mag- 

 netic action, as bismuth, but with various degrees of intensity : 

 arsenic is one of those that give the feeblest indications of possess- 

 ing this property. The following exhibit it in increasing degrees, 

 according to the order in which they are here enumerated ; namely, 

 ether, alcohol, gold, water, mercury, flint glass, tin, lead, zinc, an- 

 timony, phosphorus, bismuth. On the other hand, no gaseous 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 

 conditions among their constituent parts. Thus iron is found to re- 

 tain its magnetic power when it has entered into combination with 

 other bodies of the diamagnetic class ; the two forces acting in op- 

 position to one another, 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 certain degree magnetic, and the latter even when 

 they are held in solution 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 magnetic properties, will then be exactly neu- 

 tralized. These saline solutions, 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 especially the latter, as they admit 

 of the body under examination being suspended in another liquid, 

 when its position of equilibrium will indicate which of the two sub- 

 stances has the strongest magnetic power. 



In one respect, indeed, the diamagnetic action presents a remark- 

 able contrast with the magnetic ; and the difference is not merely one 

 of degree, but of kind. The magnetism of iron and other magnetics 

 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 



