300 BELL SYSTEM TECHNICAL JOURNAL 



of analyses which in some cases indicated the direction toward which experi- 

 ment should proceed and, in others, merely confirmed experiment, while, 

 in still others, gave answers not readily obtainable by experiment alone. In 

 the chapters that follow, the author has drawn freely on Dr. Schelkunoff, 

 particularly as regards methods of analysis. 



Beginning sometime prior to 1936, Dr. W. L. Barrow, then of the Massa- 

 chusetts Institute of Technology, also became interested in this subject and 

 together with numerous associates made very substantial contributions. No 

 less than eight scientific papers were published covering special features of 

 hollow-pipe transmission lines and electromagnetic horns. For several years 

 the work being done at the Massachusetts Institute of Technology and at 

 the Bell Telephone Laboratories probably represented the major portion, if 

 not indeed the only work of this kind in progress, but with the advent of 

 World War II, hundreds or perhaps thousands of others entered the field. 

 For the most part, the latter were workers on various military projects. 

 Starting with the considerable accumulation of unpublished technique that 

 was made freely available to them at the outset of the war, they, along with 

 others in similar positions elsewhere in this country and in Europe, have 

 helped to bring this technique to its present very satisfactory state of de- 

 velopment. 



CHAPTER VI 



A DESCRIPTIVE ACCOUNT OF ELECTRICAL 

 TRANSMISSION 



6.0 General Considerations 



The preceding four chapters presented the more important steps in the 

 development of the theory of electrical transmission, particularly as it 

 applies to simple networks, wire lines, and waves in free space and in guides. 

 For the most part, the analysis followed conventional methods and made use 

 of the concise and accurate short-hand notation of mathematics. It had for 

 its principal objective the derivation of a series of equations useful in the 

 practical application of waveguides. 



Closely associated with the theory of electricity and almost a necessary 

 consequence of it are the numerous concepts and mental pictures by means 

 of which we may explain rather simply the various phenomena observed in 

 electrical practice Tiiough extremely important, this aspect of the theory 

 was not stressed before. Instead it was deferred to the present chapter where 

 it could be considered by itself and from the purely qualitative point of 

 view. It is hoped that this arrangement of material will be of special use to 

 those who find it necessary to substitute for mathematical analysis, simple 



