340 Dynamic Theory. 



and that is the motion of some substance far more nimble than the me- 

 tallic particles of the wire conductor. 



Electric motions may take the form of gyratory movements, the same 

 as ( other ) mechanical motion, by an effect from reaction due from the 

 flowing of matter however small the quantity may be which escapes from 

 electrified substances. But the phenomenon of electrical motion is not 

 exclusively a transportation or discharge of electrified matter ; it may 

 become a molecular vibratory movement as other mechanical motion 

 does. This happens when the ponderable matter resulting from the dis- 

 charge comes in contact with a substance of a peculiar elasticity which 

 permits the transfer and propagation of the shock throughout the mass 

 of the substance. ' ' This peculiar elasticity constitutes electric con- 

 ductibility. There is not in such case an} 7 transport of ponderable mat- 

 ter throughout the length of the conducting substance, but diffusion by 

 vibrations analogous to those of the sonorous motion, or the movement 

 transferred to a series of elastic balls. The phenomenon of the jet of 

 ponderable matter may be also produced at the extremity of the con- 

 ductor when there is a break or change in material, as for example the 

 conducting wire. This transformation into vibratory motion may take 

 place, to a certain degree, in the electric discharge itself through an im- 

 perfectly conducting medium, such as ordinary or rarefied air. There 

 is then both transport and vibratory motion ; and it is this double effect 

 which often gives to electric phenomena such complicated appearances. 



The phenomena of suction produced by the flow of an electric current 

 of high tension, are analogous to those which result from the passage 

 in a narrow tube of a liquid or jet of steam impelled at a great speed 

 ( as in the Giffard Injector ). M. D. Colladon has observed an analogous 

 suction or reverse action in water-falls. He says, ' ' There may be per- 

 ceived little sheaves composed of millions of liquid pearls impelled at a 

 rapidity of motion absolutely incredible, in a contrary direction to the 

 water of the cascade, and quickly ascending towards the summit. " 

 Analogous to this says Plante, ' ' The very rapid movement of ponder- 

 able matter which constitutes electric discharge produces like the rapid 

 motion of a fluid a suction or inverse motion in the particles of matter 

 which receive the electric shock, or of that which forms the center or 

 medium of the matter traversed by the discharge. From that cause 

 a double movement occurs in two different directions, consequently a 

 double transport of ponderable matter. To this double movement are 

 due the effects produced in electric discharge, which are, by general 

 consent, called positive and negative electricity. Instead of these ex- 

 pressions, which seem to infer two sorts of electricity, the terms < ' direct 

 electric motion " and "inverse electric motion" may be substituted. 

 11 As to the phenomena produced by electricity called static, we consider 



