6l2 



PHILOSOPHICAL TRANSACTIONS. 



[ANNO 1800. 



duplicate ratio of the distance. Hence it appears, that the proposal for adopting 

 the logarithmic curve for the form of the speaking trumpet, was founded on falla- 

 cious reasoning. The calculation of M. de la Grange is left for future examination ; 

 and it is intended, in the mean time, to attempt to ascertain the decay of sound as 

 nearly as possible by experiment: should the result favour the conclusions from that 

 calculation, it would establish a marked difference between the propagation of sound 

 and of light. 



8. On the Harmonic Sounds of Pipes. — In order to ascertain the velocity with 

 which organ pipes of different lengths require to be supplied with air, according to 

 the various appropriate sounds they produce, a set of experiments was made, with 

 the same mouth-piece, on pipes of the same bore, and of different lengths, both 

 stopped and open. The general result was, that a similar blast produced as nearly 

 the same sound as the length of the pipes would permit; or at least that the excep- 

 tions, though very numerous, lay equally on each side of this conclusion. The 

 particular results are expressed in table 1 1, and in fig. 28. They explain how a 

 note may be made much louder on a wind instrument by a swell, than it can pos- 

 sibly be by a sudden impression of the blast. It is proposed, at a future time, to 

 ascertain by experiment, the actual compression of the air within the pipe under 

 different circumstances; from some very slight trials, it seemed to be nearly in the 

 ratio of the frequency of vibrations of each harmonic. 



a, is the length of the pipe 

 Tablk n> from the lateral orifice to the 



end. c, the pressure at which 

 the sound began, b, its ter- 

 mination, by lessening the 

 pressure; d, by increasing it. 

 e, the note answering to the 

 first sound of each pipe, ac- 

 cording to the German method 

 of notation, f, the number 

 showing the place of each note 

 in the regular series of harmo- 

 nics. The diameter of the 

 pipe was .35; the air duct of 

 the mouth-piece measured, 

 where smallest, .25 by .035; 

 the lateral orifice .25 by .125. 

 The apparatus was not calcu- 

 lated to apply a pressure of 

 above 22 inches. Where no 

 number stands under c, a sud- 

 den blast was required to pro- 

 duce the note. 



