1911] on RadioieUgraphy. 205 



messages were obtained without difficulty, by day as well as by night, 

 up to a distance of 4000 statute miles from Clifdeii. 



Beyond that distance reception could only be carried out during 

 niglit time. At Buenos Ayres, over 0000 miles from Clifden, the 

 night signals from both Clifden and (Jlace Bay were generally good, 

 l)ut their strength suffered some variations. 



It is rather remarkable that the radiations from Clifden should 

 have been detected at Buenos Ayres so clearly at niglit time and not 

 at all during the day, whilst in Canada the signals coming from Clifden 

 (2400 miles distant) are no stronger during the night than they are 

 by day. 



Further tests have been carried out recently for the Italian 

 Government between a station situated at Massaua in East Africa and 

 Coltano in Italy. Considerable interest attached to these experiments, 

 in view of the fact that the line connecting the two stations passes 

 over exceedingly dry country and across vast stretches of desert, in- 

 cluding parts of Abyssinia, the Soudan and the Libyan desert. The 

 distance between the two stations is about 2600 miles. 



The wave length of the sending station in Africa was too small to 

 allow of transmission being effected during day time, but the results 

 obtained during the hours of darkness were exceedingly good, the 

 received signals being quite steady and readable. 



The improvements introduced at Clifden and Glace Bay have had 

 the result of greatly minimising the interference to which wireless 

 transmission over long distances was particularly exposed in the 

 early days. 



The signals arriving at CHfden from Canada are as a rule easily 

 read through any ordinary electrical atmospheric disturbance. This 

 strengthening of the received signals has moreover made possible the 

 use of recording instruments, which not only give a fixed record of 

 the received messages, but are also capable of being operated at a much 

 higher rate of speed than could ever be obtained by means of an 

 operator reading by sound or sight. The record of the signals is ob- 

 tained by means of photography, in the following manner. A sensitive 

 Einthoven string galvanometer is connected to the magnetic detector 

 or valve receiver, and the deflections of its filament, caused by the 

 incoming signals, are projected and photographically fixed on a sensi- 

 tive strip, which is moved along at a suitable speed (Fig. 12). On 

 some of these records, which I am able to show, it is interesting to note 

 the characteristic marks and signs produced amongst the signals by 

 natural electric waves or other electrical disturbances of the atmo- 

 sphere, which, on account of their doubtful origin, have been called 



Although the mathematical theory of electric wave propagation 

 through space was worked out by Clerk Maxwell more than 50 years 

 ago, and notwithstanding all the experimental evidence obtained in 

 laboratories concerning the nature of these waves, yet so far we under- 



