246 On Magnets and Electric Conductors. [Mar. 19, 



themselves ; and 1 therefore conclude that the attractions and repulsions 

 of electric conductors are not exerted between the currents themselves, but 

 betiveen tlie substances conveying them. 



Some important consequences appear to flow from this conclusion, 

 especially when it is considered in connexion with Ampere's theory of 

 magnetism, and with the molecular changes produced in bodies generally 

 by electric currents and by magnetism. 



As every molecular disturbance produces an electric alteration in bodies, 

 so, conversely, the discoveries of numerous investigators have shown that 

 every electric current passing near or through a substance produces a 

 molecular change, which is rendered manifest in all metals, liquid con- 

 ductors, and even in the voltaic arc by the development of sounds, espe- 

 cially if the substances are under the influence of two currents at right 

 angles to each other. In iron it is conspicuously shown also by electro- 

 torsion, a phenomenon I have found and recently made known in a paper 

 read before the Royal Society. 



Numerous facts also support the conclusion that the molecular changes 

 referred to last as long as the current. De la Eive has shown that a rod 

 of iron, either transmitting or encircled by an electric current, emits, as 

 long as the current lasts, a different sound when struck ; and we know it 

 also exhibits magnetism. The peculiar optical properties of glass and 

 other bodies with regard to polarized light discovered by Faraday also 

 continue as long as the current. A rod of iron also remains twisted as 

 long as it transmits and is encircled by electric currents ; and in steel 

 and iron the molecular change (like magnetism) partly remains after the 

 currents cease, and enables the bar to remain twisted. 



That the peculiar molecular structure produced in bodies generally by 

 the action of electric currents also possesses a definite direction with re- 

 gard to that of the current, is shown by the rigidly definite direction of 

 action of magnetized glass and many other transparent bodies upon polar- 

 ized light, also by the difference of conductivity for heat and for elec- 

 tricity in a plate of iron parallel or transverse to electric currents, by 

 the stratified character of electric discharges in rarefied gases and 

 the action of electric currents upon it, and especially by the pheno- 

 mena of electro-torsion. In the latest example an upward current pro- 

 duces a reverse direction of twist to a downward one, and a right-handed 

 current develops an opposite torsion to a left-handed one ; and the two 

 latter are each internally different from the former. As each of these 

 four torsions is an outward manifestation of the collective result of inter- 

 nal molecular disturbance and possesses different properties, these four 

 cases prove the existence of four distinct molecular movements and four 

 corresponding directions of structure; and the phenomena altogether 

 are of the most rigidly definite character. , 



As an electric current imparts a definite direction of molecular struc- 

 ture to bodies, and as the attractions and repulsions of electric wires are 



