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Commendatore G. Marconi 



[March 13, 



In some of my earliest experiments, in 1896, I used copper 

 mirrors, by the aid of which it was possible to project a beam of 

 electric radiation in a certain direction, but I soon found that this 

 method would only work over short distances. 



About three years ago I again took up the subject and was al)le 

 to determine that by means of horizontal aerials, disposed in a parti- 

 cular manner, it was possible to confine the effects of electric waves 

 mainly to certain directions as desired. True, the limitation of 

 transmission to one direction is not very sharply defined, but it is 

 nevertheless very useful. The practical result of this method has 

 been so far that messages can be sent over considerable distances in 

 the desired directions, while they travel only over a comparatively 

 short distance in other directions, and that, with aerials of moderate 

 height, greater efficiency in a given direction can be obtained than 

 can be obtained all round by means of the ordinary aerials. 



When this type of aerial was adopted at Glace Bay a considerable 

 strengthening of the received signals at Poldhu was noticed. It was 

 therefore decided to adopt the directional aerial at all long-distance 

 stations. 



Fig. 12. 



A further improvement introduced at Clifden and Glace Bay 

 consisted in the adoption of air condensers, composed of insulated 

 metallic plates suspended in air at ordinary pressure. In this manner 

 it is possible to prevent the dissipation of energy due to losses caused 

 by the dielectric hysteresis in the glass dielectric of the condensers 

 previously employed ; and a very appreciable economy in working, 

 resulting from the absence of breakages of the dielectric, is effected. 

 These air condensers, which have been in use since May of last year, 

 have been entirely satisfactory. 



After very considerable delay and expense, the new station at 

 Clifden was got ready for tests by the end of May 1907, and experi- 

 ments were then commenced with Glace Bay. 



I ought to say that in the constructional and experimental work 

 carried out at the Canadian station I have received valuable assistance 

 from Mr. R. N. Yyvyan ; and at Poldhu and Clifden Mr. W. S. 

 Entwistle has assisted me in carrying out much original research 

 work, required in the designing of novel apparatus necessary for long- 

 distance transmission. Mr. P. J. Woodward has likewise rendered 

 me valuable help in the receiving arrangements, and has on nearly 

 every occasion, been in charge of the receiving apparatus during 



