WIRE TRANSMISSION THEORY 277 



To recapitulate this mode of attack, first determine the distribution 

 of line currents and charges by means of elementary theory; that is, 

 determine the principal wave distribution of currents and charges. 

 Secondly, calculate the field of this current and charge distribution 

 by means of the retarded potentials. This will give in addition to 

 the field calculable from elementary theory an additional field the 

 existence of which is not recognized by elementary theory. In brief, 

 this mode of attack is based on the argument that the actual distribu- 

 tion of current and charge in the system is given with sufficient accu- 

 racy by elementary theory, but that in calculating the field at a 

 distance, corrections must be introduced. 



As might be expected this mode of attack presents formidable 

 difficulties particularly when the ground plays an important role in 

 the transmission phenomena. On the other hand, the analysis of a 

 few of the simplest cases has been quite encouraging and leads one to 

 hope that the method may at least be successfully applied to calculating 

 the orders of magnitude of corrections which must be introduced in 

 such important problems as, for example, inductive disturbances, in 

 neighboring transmission systems. 



The foregoing may appear to many as highly academic and the- 

 oretical. The writer's actual experience with practical transmission 

 problems has convinced him, however, that the extension of wire 

 transmission theory along the lines indicated above is urgently needed. 



References 



The papers listed below represent recent work which deals directly 

 or indirectly with the problems discussed in the text. The relatively 

 large number of the writer's own papers which are listed merely 

 reflects the fact that very few specialists are working on the advanced 

 problems of wire transmission theory. 



1. "Radiation from Transmission Lines." (Carson, Jour. A. I. E. E., Oct., 1921.) 



2. "Radiation from Transmission Lines." (MannelDack, Trans. A. I. E. E., 1923.) 



3. "A Generalization of the Reciprocal Theorem." (Carson, B. S. T. J., July, 1924.) 



4. "Das Reziprotat Theorem der drahtlosen Telegraphic." (Sommerfeld, Jahrh. d. 



drahtl. Tel. u. Tel., 1925.) 



5. "The Guided and Radiated Energy in Wire Transmission." (Carson, Trans. 



_A. I. E. E., 1924.) 



6. "Ober das Feld einer Unendlich langen Wechselstromdurchfiossenen Einfach- 



leitung." (Pollaczek, E. N. T., 3, 1926.) 



7. "Electromagnetic Theory and the Foundations of Electric Circuit Theory." 



(Carson, B. S. T. J., Jan., 1927.) 



8. "A Generalized Two-Dimensional Potential Problem." (Carson, Bull. Am. 



Math. Soc, May-June, 1927.) 



9. "Electromagnetic Waves, Guided by Parallel Wires." (Levin, Trans. A. I. 



E. £., 1927.) 

 10. " Propagation of Periodic Currents over a System of Parallel Wires." (Carson 

 and Hoyt, B. S. T. J., July, 1927.) 



