SPEAKING TRUMPET. 16$ 



Art. ] 0. Though the foregoing fluents have received one Theory of the 

 correction, each of them requires a fecond, arifing from ^" '"" 

 certain circumftances peculiar to this problem. For it is 

 evident, that ihe commencement of the agitation at N is 

 prior to that at C, by a part of time, which is as C O — ON; 

 confequently the completion of the former pulfe at L, will 

 precede the termination of the latter at the fame point by a 

 fimilar interval ; which is as LC-f-C O — O L. Put this time 

 — t, and the duration of one vibration of the larynx = 1; alfo 

 let the indivifable interval, or -■§ of a fecond according to 

 Euler be denoted by m ; then multiply the expreffions in Art. 9 



by the traction — - — • 



Art. 1 1. The force determined in the preceding paragraphs, 

 is that which a non-conducting tube imparts to an evanefcent 

 fphere of air. This circumftanee affords a plaufible objection 

 to the prefent theory ; becaufe the fenfe of hearing is not con- 

 fined to a phyfical point. But as the feat of this fenfation is 

 of a given extent, at leaft in each perfon, the number of thefe 

 vibrating points, in contact with the fenfitive furface, is alfo 

 given: from this it follows, that the effect of one particle is 

 nearly a true meafure of the power of the whole number, 

 when the ear lies at a great diftance from the plane C N D, 

 reprefenting the trumpet's mouth. 



Art. 12. So much of the prefent fheet is occupied by the 

 confideration of the firft caufe, that my remarks on the fecond, 

 or the effects of the metallic (hell, muff be confined within 

 narrow limits ; thefe I fhall begin as follows. 



Art. 13. Since, the conducting power of the trumpet is 

 given, the vibrations communicated to the fmall end of it by 

 the breath and face, will pais to the oppofite extremity in a 

 given time; which call L. Alfo let h be the force of a 

 vibration at the diftance 1 ; and C L or b exprefs the fpace 

 betwixt the trumpet and a remote ear. 



Art. 14. In the firft place, let I be equal to L; then a fingle 

 pulfe of the trumpet will ftrike the ear for every vibration of 



the voice; and the force of it will be — ■- ■ - ■■ by my former 



paper on this fubject. In the next place, let I be an aliquot 



part of L; then the number of pulfes impreffed on the ear in 



M 2 the 



