1897.] HOUSTON, KP:XXELLY — THE PATH OF A CUREENT. 155 



cuited, or insulated, at both ends. The arrows v and v', represent the 

 direction in which the blocks have arrived, and the curved arrows 

 mm, and m'm^ represent the direction of magnetic flux which has 

 been generated by the movement of each block, and which has 

 been carried bodily along with the moving blocks. If the original 

 metre block of flux in Fig. 4, represents an amount of energy resi- 

 dent in electric flux, amounting to say 1000 ergs, then each of the 

 two metre blocks into which this is divided, assuming no dissipation 

 of energy, carries with it 500 ergs, 250 in magnetic flux and 250 in 

 electric flux. 



Fig. 8 m m' 



g iuiiiit^^ ZL^-lMj) 



m ni' 



F/g.9 



^j(Mu7_ _aJMj) 



Figs. 8-10. — Reflected Movement of Electric Flux in Circuit of Perfect Conduc- 

 tion and Insulation, 



On arrival at the termini, the flux is compressed into a half metre 

 at each end, as represented in Fig. 9. The density of electric flux 

 IS doubled, as represented by the closeness of the arrows. At the 

 same time the magnetic flux vanishes, while the pressure rises 

 momentarily from 500 to 1000 volts. There is, therefore, half the 

 volume of flux with twice the density; and, therefore, four times 

 the voluminal electric energy, but no magnetic energy. Conse- 

 ruently, there remains 500 ergs of purely electric energy in each 

 block. 



Fig. 10, represents the conditions of afl'airs immediately after- 

 wards. Here the blocks expand again into metre lengths and are 

 reflected from the termini, or move back towards the centre of the 

 line. The magnetic flux reappears, but in the reversed direction, 

 as shown by the curved arrows. The electric flux retains its origi- 

 nal direction from the upper to the lower wire, and the pressure has 

 fallen from 1000 to 500 volts as before. The current represented 



