1020 Dynamic Theory. 



Then again in galvanic processes such as electrolysis, there seems to be 

 a progressive movement of a substance from one place to another, a 

 current in the true sense of the term. But in the radiation of light 

 and heat, while there is not supposed to be a bodily movement of the 

 ether in the form of a current, there is an advance of an undulatory 

 movement of the molecules, beginning at the luminous body and spread- 

 ing in all directions. So that a streak of light is a progressive succes- 

 sion of local molecular movements. Something similar to this has been 

 suggested as the mode of the propagation of electrical attraction. A 

 body positively electrified begins its inductive operations upon the mole- 

 cules of ether next to it. by driving off the positive electricity in them 

 to their further end, and attracting the negative electricity in the near 

 end. The repelled positive electricty performs the same operation upon 

 the next molecules, and so on. In case ponderable bodies are involved, 

 the end next the original attracting positive body being nearer than the 

 repelled end, the balance is in favor of attraction, and so the body 

 moves toward the attracting body. It may be observed further that as 

 the repelled electricity is always on the peripheral portion of concentric 

 spherical shells, it must be less intense area for area, than the inner or 

 attracted electricity. (See illustration of sound page 374). So that 

 as between attraction and repulsion the balance is always in favor of 

 the former. 



Electrical repulsion takes place after a negative body has been at- 

 tracted and held awhile in contact with a positive body, the presumption 

 being that positive electricity is transferred to the negative body until it 

 becomes more positive than negative, when the two being alike, repel. 

 We do not see this repulsion as between permanent magnets and the 

 bodies they attract. The armature of a horse shoe magnet is drawn to 

 the poles and remains there for years. There is repulsion however, if 

 poles of separate magnets having the same name are brought near each 

 other. But it takes work outside of the bodies concerned to bring 

 about such presentation of opposing poles. Thus there appears to be 

 no difference in principle between electricity and magnetism in this re- 

 spect, but the differences depend upon the bodies involved. No body 

 becomes either electrified or magnetized unless work is expended upon it. 

 The work expended upon most bodies in electrifying them by friction is 

 soon expended in processes of repeated repulsion, or in the recovery of 

 its former neutral condition by the electrified body-. When work is ex- 

 pended in setting up magnetic action in a piece of steel, however, it is 

 like setting a top to spin in a vacuum; it runs for a long time before 

 the force is wasted. The attractive force of the magnet is limited to 

 to the amount of energy expended in making a magnet of it, and if it 

 be loaded with a weight which the same quantity of energy could raise 



