Electric Residue in the Ley den Jar, 423 



It would be difficulty however, by this method of representation, 

 to show why the thicker plate should fm-nish the greater residue. 

 Let us therefore consider the second. 



2. Electricity does not pass from one pai'ticle of glass to 

 anothei", but either separates itself on each particle, as in the 

 case of magnets, or was already separated on these particles, and 

 the latter, together with the electricities clinging to them, are 

 turned. In the fii'st hypothesis, a force must be attributed to 

 the several particles of glass, which only permits the separation, 

 and the corresponding motion, to take place gradually, and which 

 resists it the more the longer it is prolonged, so that the limit of 

 the residue has herein its cause. Although in this case the 

 molecular forces might play the part of resistance, inasmuch as 

 with the separation of the electricities a simultaneous displace- 

 ment of the atoms might be connected, yet it is clear that a more 

 natural explanation of the slow change of condition, and of the 

 maximum results from the last hypothesis, i. e. that the atoms 

 are tui'ned, and that the molecular forces, as in bends, torsions, 

 &c., resist this turning. And if we consider the phaenomena of 

 elasticity as a whole, we shall soon find a circumstance which 

 has great similarity with the one here mentioned, and which in 

 its way stands single. This is the so-called elastic secondary 

 action, which has been made known to us by W. Weber*, through 

 his researches on silken threads (the only complete research 

 which exists on this subject). 



Probably all bodies possess this elastic secondary action ; at 

 least glass certainly does sof. The phsenomenon may be thus 

 characterized : — 



When the form of a body is changed through the influence of 

 some external force, without however surpassing the limits of 

 perfect elasticity, the new state of equilibrium within the body, 

 and hence also the change of form, will require time to establish 

 itself; will, in fact, establish itself asymptotically after an inde- 

 finitely long period. At first the form changes quickly, after- 

 wards very slowly. The subsequent slow change has been de- 

 signated the "elastic secondary action," although the latter, as 

 W. Weber i-emarks, is separated by no natural limit from the 

 quicker change, for the velocity of the change of form does not 

 anywhere decrease discontinuously. If the external action which 

 produced the change of form cease, the body will assume the 

 same series of forms, only in inverse order and with an opposite 

 velocity ; only after a long time (indefinitely loug) will it per- 

 fectly recover its original form, In these wonderful phainomena, 

 where the velocity of the moved mass bears no proportion to the 



* De fill bomhycini vi elasticu. Gottingse, 1841. 

 t Poggcndortl's Annalen, vol. Ixxii. p. .'^y3. 



