MAGNETISM. 1 



cal affinity and light, though, up to the present time, such I 

 not been proved to be the case ; the reciprocal effect, also, 

 the direct production of magnetism by light and heat has r 

 yet been experimentally established. 



I have used, in contradistinction, the terms dynamic a 

 static to represent the different states of magnetism. 1 

 applications I have made of these terms may be open to so 

 exception, but I know of no other words which will so nea 

 express my meaning. 



The static condition of magnetism resembles the sta 

 condition of other forces : such as the state of tension exi 

 ing in the beam and a cord of a balance, or in a charg 

 Leyden phial. The old definition of force was, that wh: 

 caused change in motion ; and yet even this definition p 

 sents a difficulty : in a case of static equilibrium, such, 

 instance, as that which obtains in the two arms of a balan 

 we get the idea of force without any palpable apparent motio 

 whether there be really an absence of motion may be a dou 

 ful question, as such absence would involve in this case p 

 feet elasticity, and, in all other cases, a stability which, ii 

 long course of time, nature generally negatives, showing, 

 I believe, an inseparable connection of motion with matt 

 and an impossibility of a perfectly immobile or durable sta 

 So with magnetism: I believe no magnet can exist in 

 absolutely stable state, though the duration of its stabil 

 will be proportionate to its original resistance to assumi 

 a polarised condition. This, however, must be taken mer< 

 as a matter of opinion : we have, in support of it, the gene] 

 facts that magnets do deteriorate in the course of years ; a 

 we have the further general fact of the instability, or fluxioi 

 state, of all nature, when we have an opportunity of fai] 

 investigating it at different and remote periods : in ma 

 cases, however, the action is so slow that the changes esca 

 human observation, and, until this can be brought to be 

 over a proportionate period of time, the proposition cannot 



