SPEAKING TRUMPETS. 2^h 



XVI. 



Obfervations on the Caufe which augments the Jnteiifity of the 

 Somdin Speaking Trumpets, ^j^ J. H. Hassenfratz *. 



^ALTHOUGH the I'peaking-trumpet is an inftrument which Anriquity of the 

 has been long known, fince Kircher is of opinion that Alex- ^ *"* ^'^*"^' 

 ander ufed it to command his army, and Solard made one in 

 Paris, in I654f, from the defcription which Kircher had given 

 of that of Alexander, it was not, however, until 1671, when 

 Morland made known that which he had conftru6led, and in- MorIand*s« 

 vited men of fcience to determine the figure mofl proper for 

 this inftrument, that the fpeaking-trumpet was really known 

 among us, and began to be ufed. 



It appears that Morland did not adopt the conical form ter- 

 minated by a mouth piece, which he gave to the fpeaking trum- 

 pets of glafs, iron and copper, he made until after a fucceffion 

 of trials on the beft form to be given to them, lo make them 

 produce articulate founds. 



It alfo appears that it was without knowing it, and by chance, Caflegrain's, 

 that Caflegrain gave the fpeaking trumpet, which he made in 

 J 672, the hyperboloidal form firft noticed by Sturm. 



Until 1719, when Haflfe publiftied a diflertation on the im- Were at firft 

 provement of fpeaking trumpets, this inftrument was con- *^""^^ VT 

 ftruded without principles; for we neither can nor ought to principles, 

 confider as principle, the harmonic proportion mentioned by 

 Caflegrain as being neceflary between the length and the width 

 of the tubes of fpeaking trumpets. 



The law of the refledion of found in echoes, led Haffe to Haffe's theory 

 apply the theory of catoptrics to fpeaking trumpets, and in- "^5^^ ^"^["^"' 

 duced hira to confider the combination of the ellipfoidal and intenfity of 

 paraboloidal forms as the moft advantageous for this inftrument : ^^^^'^ ^ ^^^"** 

 but this union not producing the efte<ft which the profelfor of 

 Wirtemberg had hoped for, it was abandoned, and in conform- 

 ity with his opinion, the augmentation in the intenfity of the 

 found continued to be confidered as (he product of the reflec-. 

 tion of the fonorous rays in the fpeaking trumpet, and of the 

 vibration of the fubftance of which it was compofed. It wks 

 for this reafon that, in the fabrication of thefe inftruraents, the 



• From Annales de Chimie, Pralreal, An. XII. 



attention 



