abstracts: radiotelegraphy 641 



takes place, than from the side-walls. Glass melted in these pots 

 showed, in all cases but one, less iron than that made in untreated pots. 

 In the exception noted above, however, more iron was found in the 

 glass made in the treated pot, and it was shown that, although the iron 

 had been volatilized from the pot, more than usual pot corrosion had 

 taken place during melting. The success of the method, then, depends 

 on whether a dense surface can be made in such pots when the iron has 

 been removed, as, for instance, by burning under different conditions 

 from that obtaining during the course of these experiments. With 

 some types of pots the method would undoubtedly be successful, even 

 with the usual burning schedules. The possible application to the re- 

 moval of iron from grog, clay, and other ceramic products is indicated. 



J. C. H. 



RADIOTElvEGRAPHY. — Principles of radio transmission and re- 

 ception with antenna and coil aerials. J. H. Dellinger. Proc. 

 Amer. Electr. Eng. 38: 1095-1150. 1919. 



Coil aerials are coming to replace the large antennas in radio work. 

 The advantage of the coil aerial as a direction finder, interference pre- 

 venter, reducer of strays, and submarine aerial, make it important to 

 know how effective such an aerial is as a transmitting and receiving 

 device in comparison with the ordinary antenna. In this article the 

 mathematical theory is presented and, as a result, the answer 

 to this question is obtained. Experiments have verified the conclu- 

 sions reached, and the formulas which are obtained are a valuable aid 

 in the design of an aerial to fit any kind of radio station. 



It is found that the coil aerial is particularly desirable for communica- 

 tion on short wave lengths-. A coil aerial is as powerful as an antenna 

 only when its dimensions approach those of the antenna. For other 

 reasons, however, a small coil aerial is in many cases as effective as a 

 large antenna. It is shown that an advantageous type of radio aerial 

 is a condenser consisting of two large metal plates. This type of aerial 

 has many of the advantages of the coil aerial. The fundamental 

 principles of design of aerials are given in the paper. On the basis of 

 this work the actual functioning of any type of radio aerial can be de- 

 termined either from measurements made upon the aerials or from ac- 

 tual transmission experiments. J. H. D. 



