Influence of Temperature on Magnetism. 213 



by elevation of temperature had led several philosophers to 

 believe that the property possessed by certain bodies of being 

 magnetic, was due to the small distance existing between 

 the atoms of which they are formed. 



In fact, iron, cobalt, and nickel, are among those bodies which, 

 under the same volume, contain the greatest number of atoms, 

 and consequently are those whose atoms are the nearest to- 

 gether. To heat these bodies is to remove their particles from 

 each other; now, since this increase of distance makes them lose 

 their magnetic properties when it is carried to a certain point, 

 it follows that the substances among which the atoms are na- 

 turally more apart cannot possess these properties. What 

 must be done, then, to make them acquire these properties % 

 We must bring the particles nearer, and, for this purpose, 

 must cool these bodies. Guided by this ingenious idea, Fara- 

 day had exposed, to an exceedingly low temperature, the 

 greater part of the metals, and several of their compounds, 

 and also carbon ; and, notwithstanding he acted upon them 

 with a very powerful magnet, he was unable to discover any 

 trace of magnetism ; he had the precaution to take all these 

 bodies in a state of great purity, and deprived of all traces 

 of iron. By means of a mixture of ether and carbonic acid 

 placed in a vacuum, he succeeded in reducing their tempera- 

 ture to 105° cent, below 0°. Manganese itself presented no 

 trace of magnetism. Mr Faraday has shewn that it is to the 

 presence of a few particles of iron, of which it is a difficult 

 matter to deprive it, that this metal had hitherto been errone- 

 ously classed among those which are magnetic. Thus, iron, 

 nickel, cobalt, and steel, would seem to be the only bodies in 

 nature that are magnetic, that is to say, that present mag- 

 netic properties, such as we have just studied and denned 

 them. Faraday has arrived, by other means, to discovering 

 equally in all bodies evident magnetic properties, but vari- 

 able, in the form under which they are manifested, with the 

 nature of the bodies themselves. — {A Treatise on Electricity , 

 by A. de la Rive, vol i., p. 174.) 



