164 SPEAKING TRUMPET 



Theoryofthe _ i| . £ , T . L , it _ f h m d* 



fpe; 

 pet 



fpealcing trum- the time of L is ^--; hence the force -■■■ « . Add this 



equation to the former of thole found in /2r£. 9 ; and the fum 

 gives the force of the trumpet upon a diftant ear. 



Art. 15. But if / be an aliquant part of L, the found will 



be imperfectly formed ; becaufe the quantify — — being a mixed 



number, the vibrations of the larynx will be conducted along 

 the metal, and discharged into the air in a diiorderly manner, 

 fo as to deftroy the continuity of the note. The fame caufe, 

 in all probability, conftitutes the difficulty which the inex- 

 perienced find in their firft attempts to found horns and 

 military trumpets: for the lips, which are compreffed by the 

 end of the tube, form the mouth piece in this cafe ; and the 

 art of producing the found feems to confift in caufing the 

 edges of them to vibrate in aliquot parts of L, or the interval 

 belonging to the loweft note of the inftrument. The fame 

 origin may alfo be afcribed to the mufical fcale, compofed of 

 what are called the trumpet notes; the intervals of which 

 decreafe in the following ratios, 1, i, ^, i, |g &c. for i. is 

 the greateft aliquot part of unity, ^ the next in fucceffion, and 

 fo on. 



Art. 16. If the remarks contained in the two preceding pa. 

 ragraphs be juft, the perfon who makes ufe of a fpeaking 

 trumpet, muft attend to the management of his voice; the 

 pitch of which ought to coincide with fomenote in the trumpet 

 fcale of his inftrument : for proper attention to this circum- 

 ftance will make the found of the metallic (hell perfect, and 

 bring it into unifon with the other found ; which arifes from 

 the aerial pulfes, paffing through the cavity of the tube, at the 

 fame inftant. In this manner, the greateft found will be pro- 

 duced, fuppofing the power of the voice to be eonftant; be- 

 caufe the two lets of pulfes, conftituting the unifon, will im- 

 prefs the greateft poffible force upon the ear in a given time. 

 On the other hand, if the foregoing precaution be neglected, 

 the imperfect found of the metal will difturb the uniformity 

 of the other, which is formed in the cavity ; and the force im- 

 preffed on the ear by fo diforderly an aggregate of pulfes, 

 will be interrupted and inconftant. 



Art. 17. Perhaps it is unneceffary to remark, that the perfect 

 elafticity of the air forms the bafis of the prefent theory; a 



fuppofition 



