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XT. Letter from E. Perolle cf the Acailrmy of Turing 

 Jornii-rlv ProfefJ'or of Anatomy and the VraB'icc oj Mcdic'im 

 at Touloufe, to J. C, DK LA Metukrie, o« the AcoujUc 

 Experiments o/'Chladni *. 



I 



Read in your Journal of Meffidor, (5th year, and in the 

 Bulletin des Sciences, publifhed by the Philomatic Society of 

 Pkiviofc the fame year, a fhort account of the experiments 

 jnade by Chladni and Jacquin at Vienna, with a view to 

 tietermine the fonorous properties of various gaf^dus fub- 

 (lances. By cauling a fmall tin pipe, brought into contaft 

 with a cock in the neck of a bell glafs, to be blown by gas 

 contained in a bladder applied to the external aperture of the 

 cock, thefe philofophers obferved, that the found was a femi- 

 tone lower with azotic and oxygen gas than with atmofpheric 

 air; a third lower with carbonic acid gas; and nearly the 

 fame with nitrous gas : but, with oxygen gas, from nine ta 

 eleven tones higher than with the air that furrounds us. A 

 mixture of azote and oxygen, in the fame proportions as in 

 atmofpheric air, gave the fame tone as the latter; but when 

 the mixture of thefe gafes was not uniform, the founds were 

 totally difcordant. The fmgularity of thefe refults induced 

 me to examine the experiments with attention. 



Prieftlcy t, feveral years ago, publiHied fome obfervations 

 on the fame fubjedrl: ; but he had made ufe of a metallic body 

 rendered fonorous by percuflion, after he had fixed it in a glafs 

 jar, which he filledfucceffively with different kinds of gas. The 

 aeriform fubflances which he employed for his experiments 

 appeared to him to propagate founds in proportion to their 

 dcnfity : he remarked, that in hydrogen gas the found feemed 

 like that produced in a vacuum or air highly rarefied. Is it 

 to be fuppofed that fuch a philofopher as Pricftley w^ould have 

 failed to difcover the alteration of tones produced in the va- 



• From tlic Journal Ue Pbyjique, an. 7. 



f See Qhf'rvaliens and Expcrimenti on d'rffnent Bianchei of PhUofophy, 

 Part III. p. 355. — rrieftlcy mudc no cxpeiimcuib with nitrous gas. 



rious 



