On Electric Waves along Parallel Wires. 643 



would suggest that either the resistance of the spark for the 

 most part is due to the passage from the electrodes into the 

 surrounding gas, or that; the section of the spark augments 

 as its length increases. 



3. The resistance of a wire bent to a spiral is for oscil- 

 latory discharges much higher than that shown by the same 

 wire when stretched out into a straight line. 



The difference between the two values augments as the 

 frequency of the discharge increases and the distance between 

 the single spires decreases. Lord Rayleigh's formula thus 

 does not apply to circuits bent into a spiral. 



4. The sum of the calorific energies spent by the discharge 

 in the spark and the metallic circuit agrees fairly well with 

 the value of the energy of the condenser. 



5. With cadmium electrodes the sparks are much more 

 regular than those corresponding to platinum and platino- 

 iridium electrodes. 



6. The values of the spark-resistance and of the energy 

 spent in the spark itself are, in the conditions of our experi- 

 ments, practically identical for platino-iridium and cadmium 

 electrodes. \ 



LXVI. On the Connexion between Speed of Propagation and 

 Attenuation of Electric Waves along Parallel Wires. By 

 W. B. Morton, M.A., Professor of Natural Philosophy, 

 Queen's College, Belfast*. 



w 



/'HEN electric oscillations, of frequency ■—-, are guided 



by imperfectly conducting leads, the various vectors contain 

 a factor 



*(! 



2 f-^«) 



the propagation being along the positive direction of the axis 

 of z. The course of the analysis leads, in general, to an ex- 

 pression for the complex quantity m = -~ — |- i/c as a function 



A 



of p and of the magnitude oy --- , where a is the radius 



of the wire, (jl the permeability, and p the resistivity of it> 

 material. 



In the present paper I start with the approximate formula 

 for m in the case of two parallel wires, as discussed in former 



* Communicated bv the Author. 



