146 CORRELATION OF PHYSICAL FORCES. 



tion of which must be left to the future ; at present, the an- 

 swer to it would depend upon the theory we adopt. If the 

 view of light and heat which I have stated be adopted, then 

 we may fairly say that magnetism, in these experiments, di- 

 rectly affects the other forces ; for Alight and heat being, ac- 

 cording to that view, motions of ordinary matter, magnetism, 

 in affecting these movements, affects the forces which occa- 

 sion them. If, however, the other theories be adhered to, it 

 would be more consistent with the facts to view these results 

 as exhibiting an action upon the matter itself, and the heat 

 and light as secondarily affected. 



When substances are undergoing chemical changes, and a 

 magnet is brought near them, the direction or lines of action 

 of the chemical force will be changed. There are many old 

 experiments which probably depended on this effect, but 

 which were erroneously considered to prove that permanent 

 magnetism could produce or increase chemical action : these 

 have recently been extended and explained by Mr. Hunt and 

 Mr. Wartmann, and are now better understood. 



The above cases are applicable to the subject of the pres- 

 ent Essay, inasmuch as they show a relation to exist between 

 magnetic and the other forces, which relation is, in all proba- 

 bility, reciprocal ; but in these cases there is not a production 

 of light, heat, or chemical affinity, by magnetism, but a change 

 in their direction or mode of action. 



There is, however, that which may be viewed as a dy- 

 namic condition of magnetism ; i. e. its condition at the com- 

 mencement and the termination, or during the increment or 

 decrement of its development. While iron or steel is being 

 rendered magnetic, and as it progresses from its non-magnetic 

 to its maximum magnetic state, or recedes from its maximum 

 to zero, it exhibits a dynamic force ; the molecules are, it 

 may be inferred, in motion. Similar effects can then be pro- 

 duced to those which are produced by a magnet whilst in mo- 

 tion. 



