162 HOUSTON, KENNELLY — THE PATH OF A CUKRENT. [Mar. 19, 



Here the original metre blocks have diminished considerably in 

 density, and in their stock of energy, their motion being indicated 

 by the arrows Vg and v^. 1I2 and u'2, are arrows representing the mo- 

 tion of the straggling flux, or tails, as they have been called, thrown 

 off bv the advancing blocks. After a certain distance has been 

 traversed by these blocks they become completely absorbed and 

 the tails only remain, the subsequent motion being very complex. 



All the best electric conductors with which we are acquainted ; 

 namely, the metals, conduct imperfectly at the temperatures at 

 which they exist on the earth. It has been shown that pure copper 

 would apparently conduct to perfection, or have no electric resist- 

 ance, at the temperature of absolute zero, or — 273° C. It is pos- 

 sible that some means may eventually be found to artificially pro- 

 duce in copper, at ordinary temperatures, the electric conducting, 

 power it possesses at or near the absolute zero of temperature, but 

 at the present time we have to content ourselves with the compara- 

 tively imperfect conducting power of copper, which is practically 

 the best electric conductor available. Consequently, we cannot 

 attain in practice to the distortionless transmission of electro-mag- 

 netic waves such as represented in Figs. 4 to 19. 



It is, however, possible to so unite imperfect insulation with im- 

 perfect conduction; /. e., leakage with conductor- resistance, as to 

 cause the tailings due to leakage to exactly annul the tailings due 

 to conductor resistance; for, the comparison [of Figs. 20, 21 and 

 22, with Figs. 23, 24 and 25, will show that these tailings are 

 oppositely directed as regards electric flux, the tailings from leak- 

 age being reversed, and the tailings from conductor resistance 

 being similarly directed, to electric flux in the main blocks. A cir- 

 cuit in which the leakage and conductor resistance are so balanced 

 as to leave no tailings, is called a distortionless circuit, and no other 

 means of obtaining a distortionless circuit is known at the present 

 time. Although such a circuit is distortionless, since no tailings are 

 left, as the blocks of flux move on without leaving stragglers, yet en- 

 ergy is expended both into the insulator and into the conductor, and, 

 consequently, the fluxes diminish in density and attenuation goes 

 on. This is represented in Fig. 26. Here the metre block of flux is 

 started from the centre of the line as before, the directions being 

 indicated by the arrows. In Fig. 27, the electric flux is seen to- 

 have a double curvature, being partly bent outwards and partly bent 

 inwards. Energy is being dissipated sideways into the insulator. 



