138 EECENT ADVANCES IN WIRELESS TELEGRAPHY. 



news service. It has also been used to a large extent in the tests 

 across the Atlantic Ocean. 



As already stated, the adoption of this magnetic receiver was the 

 means of bringing about a great improvement in the practical work- 

 ing conditions of wireless telegraphy by making it possible to do away 

 with the troublesome adjustments necessary when using coherers, and 

 also by considerably increasing the speed at which it is possible to 

 receive, the speed depending solely on the ability of the individual 

 operators. Thus a speed of over 30 words a minute has been easily 

 attained with the apparatus as shown in fig. 12. 



This form of magnetic receiver, however, presented a disadvantage 

 which some people considered very important — of being able to bring 

 about only an audible reproduction of the signals in a telephone, and 

 consequently ineffective for actuating a recording instrument, such as 

 would leave a documentary proof in the form of Morse signals received 

 and inscribed on tape. 



When the author had the honor to deliver his last lecture at the 

 Royal Institution, he expressed a hope that by means of this magnetic 

 receiver it might be possible to work a recording instrument, and he 

 is glad to be able to announce that he has recently been able to con- 

 struct a magnetic receiver that will work a relay and a recorder. 



The causes which prevented the author's earlier type of magnetic 

 receiver from working a relay were the rapidity and alternating 

 character of the current induced by the effect of the oscillations on 

 the iron. This current or impulse is so sudden that, although it 

 proves to be suitable in producing a sound or click in a telephone 

 diaphragm, it is far too quick to impart any appreciable movement 

 to the comparatively heavy tongue of a relay, and in that way to 

 allow a current to work a recording or other instrument. By modi- 

 fying the circuits, especially by increasing their length and by the 

 use of a particular quality of iron, the author has been able to obtain 

 an impulse from the magnetic receiver, which is capable of working a 

 recording instrument. 



The instrument is eminently adapted for receiving messages from 

 stations such as Poldhu, where the length of wave radiated is con- 

 siderable. 



Tlie advantages of this receiver over the coherer system of receiver 

 are very great. 



In the first place, it is far more simple, requires far less attention, 

 is absolutely reliable and constant in its action, and possesses a low 

 and unvarying resistance. But the chief advantage lies in the fact 

 that with this receiver it is possible to attain a very high speed of 

 working. 



The speed of the author's earlier form of magnetic receivers was 



