641 



in general, wliicli could not be observed heretofore, since no vibrating 

 string with so small a decrement lias ever been available. Suppose, 

 that the vibrations of a string of a |)iano or a violin die awaj as 

 slowly as they do in the galvanometer, e.g. within about 2 oi' 3 

 sec. and that the frequency is a hundred times less, then accordingly 

 the decrement is 'JOO-times greater, for we have 



''=w, ■ ''> 



where <f and N^ have the same meaning as in form. (I) whereas 

 T represents the time in seconds necessary for tiie amplitude to 



diminish in the proportion of 1 : — . For the time of dying away 



e 



we may allow 3 to ö-times the value of t. 



The musical string therefore vibrates much les.s freely, and we 

 cannot tune it as sharply. However this is really unnecessary for 

 the purpose it is used for, since the human ear is unable to dis- 

 criminate so minute variations of pitch. The increase of tension 

 experienced by the musical string, when moving from the position 

 of equilibrium to that of the nuixiinum displacement, may be left 

 out of account at least when the amplitude is moderate. Every 

 theory of the movement of strings is based on the supposition that 

 in the different phases of a period of the vibration the tension of 

 the siring remains constant. ') 



However the conditions of the string of the galvanometer aie 

 different. A small amplitude, foi' instance to an amount of 1 per 

 thousand of the length of the string, may be sufficient under definite 

 conditions to display the influence exeited by the increase of the 

 tension which the string is subjected to by its displacement. 



We hope later on to revert to these phenomena, which may be 

 referred to as those of the "jumping point". But it should be noticed 

 here, that the difficulties caused by it are diminished to a large 

 extent and practically overcome when the string which is to be in 

 tune with a certain wave, is made as long as possible and extended 

 to a maximum. 



In fig. 5 a record made in Leyden is reproduced, whicli is of 

 special interest for ns in Holland; it represents the signals received 

 from the alternator on the Malabar at Bandoeng. In order not to 

 disclose the secret of the telegram only a few separate words and 

 figures are given, so that the meaning will be understood bj' none. 



1) Conf. Rayleigh. The theory of sound, London 1877. Vol. 1, p. 36 and 128. 



42 

 Proceedings Royal Acad. Amsterdam. Vol. XXVI. 



