647 



But it is not only with a slow transmission tiiat the string is 

 superior. If, in relation vto the disturbances, the signals are strong 

 enongli to make a record of them with a moderate or even a large 

 string decrement, then high speeds of transmission will become 

 possible and soon the Mareonist will no more be able to read the 

 signals, while the galvanometer is recording easil}' a few hundreds 

 of words per minute. 



Dr. DE Ghoot of Bandoeng, to whom we are much indebted, has 

 suggested a valuable idea. For his enthusiastic collaboraiion in the 

 difficult expeiinients carried on at Bandoeng with the galvanometer 

 some lime ago, we thank him heartil}' here. 



Dr. DE Gkoot has suggested the ap|)iication of two galvanometers 

 simultaneously when an arc generator be used for transmission ; one 

 string may be put in tune with the active wave, the other with the 

 wave of rest. An atmospheric appearing at a given nuuTient may 

 be easily recognized as such, if it influences the registration of only 

 one of the two waves. Thus the possibility of making the signal 

 readable throughout the aimospheric disturbances will become gi'eater. 



In fig. 6 a record is re|uoduced which has been made at Leyden 

 according to the suggestion of Dr. de Groot. The string of one 



Fig. 6. 



Record of the arc generator F L, Paris with 2 galvanometers 



in parallel. The signalling wave is registered by one, the non 



signalling wave by the other galvanometer. 



galvanometer is seen vibrating every time the oilier is standing still 

 and vice versa. How great the practical value of this method will 

 be has yet to be determined, but the first impressions which we 

 have obtained from the resnlt of a few experiments are favourable. 



The idea of using 2 galvanometers simultaneously may find another 

 application when signals are to be received, the wave-length of 

 which is not very constant. Either string may be put iti tune with 

 a different wave; one with a wave which is a little longer, the 

 other with a wave, which is a little shorter than the mean length 

 around which the transmission wave is fliictnating. So the admissible 

 range of fluctuation is increased, while the decrement of the vibrations 

 of either string may remain small. 



However, rather than applying this, afier all, souiewhat defective 



