MAGNETISM. 131 



have 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 pre- 

 sent 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 alone, but a 

 change in their direction or mode of action. 



There is, however, that which may be viewed as a dynamic 

 condition of magnetism ; i.e. its condition at the commence- 

 ment and the termination, or during the increment or decre- 

 ment 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 produced 

 to those which are produced by a magnet whilst in motion. 



An experiment which I published in 1845 tends, I think, 

 to illustrate this, and in some degree to show the character of 

 the motion impressed upon the molecules of a magnetic 

 metal at the period of magnetisation. A tube filled with 

 the liquid in which magnetic oxide of iron had been prepared, 

 and terminated at each end by plates of glass, is surrounded 

 by a coil of coated wire. To a spectator looking through this 

 tube a flash of light is perceptible whenever the coil is elec- 

 trised, and less light is transmitted when the electrical current 

 ceases, showing a symmetrical arrangement of the minute par- 

 ticles of magnetic oxide while under the magnetic influence. 

 In this experiment it should be borne in mind that the par- 

 ticles of oxide of iron are not shaped by the hand of man, as 

 would be the case with iron filings, or similar minute portions 

 of magnetic matter, but being chemically precipitated, are of 

 the form given to them by nature. 



While magnetism is in the state of change above described 

 it will produce the other forces ; but it may be said, while 

 magnetism is thus progressive, some other force is acting on 

 it, and therefore it does not initiate : this is true, but the same 

 may be said of all the other forces ; they have no commence- 

 ment that we can trace. We must ever refer them back to 



K 2 



