1907.] on Recent Contributions to Electric Wave Telegraphy. 703 



voice to be some day transmitted from the shores of England or the 

 United States to an xitlautic liner in mid ocean. 



We may consider in the next place another problem of great 

 practical importance, towards the solution of which some consider- 

 able progress has been made, viz. that of locating the direction of 

 the sending station, and giving direction to the emitted radiation sent 

 out from it. The early attempts to do this depended upon the use 

 of parabohc mirrors, or some arrangement of vertical rods equivalent 

 to it. But although comparatively short electric waves of a few feet 

 in wave length can be directed in this manner in the form of a beam, 

 it is out of the question for electric waves hundreds of feet in length, 

 because reflection can only take place when the dimension of the 

 mirror are at least comparable with that of the wave length. 



The ordinary vertical antenna, of com'se, radiates equally in all 

 directions, and when it is so far off as to be below the horizon a 

 corresponding receiving antenna may respond to it, but cannot locate 

 the position of the sending station. 



It seems to have been noticed by several persons that if the 



To Induction 

 Coil 



wmmmmm^mmm^m^mm^m. 



Fig. 16. — Marconi Bent Antenna. 



antenna is not vertical, it radiates rather more in one direction 

 than another, and the same for a non-vertical receiving antenna. 

 It is more receptive to waves coming from one direction than 

 another. Various observations on the operation of non-vertical, 

 looped, or duplex antennae have from time to time been made by 

 Zen neck, Sigsfeld, Strecker, Slaby, and de Forest, whilst methods for 

 locating the sending station or directing the transmitted waves were 

 described in patent specifications by de Forest, Garcia, and Stone. 

 Although claims were made for arrangements said to be effective, 

 these various researches were not pressed to such logical issue as to 

 disclose any definite general scientific principle, whilst in some cases 

 the results said to have been obtained are clearly in contradiction to 

 well ascertained facts. 



Time will not permit further reference to these early and in- 

 conclusive observations. 



In March last year Mr. Marconi communicated to the Royal 

 Society a paper on the radiation from an antenna having a short part 

 of its length vertical and the greater part horizontal, and on the re- 

 ceptive powers of a similar antenna in various azimuths (see Fig. 16). 



