sS5 On the Acoujl'ic litxperlments of Chlaihiu 



not to be carried to eleven ; or the found is fliarper by ele;v«;ii 

 tones in the hydrogen than in atmofpheric air, and then 

 it is wrong to fay that it rifes only nine tones. 



This want of corredtnefs and precifioii in determining the 

 tone ; this great latitude allowed to the hydrogen, of being 

 able to raife the found nine or eleven tones ; does it not 

 prove an indecifion, an uncertainty on the part of thcfe phi- 

 lofophers, little calculated to procure confidence to their 

 experiments ? 



Let it not, however, be imagined, that I wifli to conteft 

 the reality of their difcoverics. Not having repeated the ex- 

 periments of thcfe authors, I can have no fuch intention. 

 I have only endeavoured to give an account of thofe doubts 

 which remained on my mind after I had taken the fubjeft 

 into confideration, and to engage the philofophers to re- 

 move the uncertainty by repeating the experiments. 



One of thefe authors, Chladni, has made an obfervation 

 which feems entirely his own. He obferved, that when a 

 plate of glafs is agitated by means of a bow, if fome duft is 

 ftrewed over the glafs, the former will appear to have ar- 

 ranged itfelf fymmetrically, after the plate ceafes to emit 

 found. Under the like circumftances the figures are always 

 the fame. 



It is not at all furprifing, that an elafiic body, when put 

 in motion by the fame means, ihould conftantly experience 

 effedls of the fame kind. The light body placed on the fur- 

 face of the glafs with which the experiment is made, only 

 confirms what we were already taught by reafon. But be- 

 fore it be concluded that ihefe motions produce found, or 

 tend to determine the tone, philofophers are invited to read 

 my Letter to Dc la Metherie On the Total Vibrations of 

 So)iorous Bodies, publiOied in the Journal de Vhyjiqrie for 

 Decem.ber 1785. This letter, the fenfe of which is altered by 

 fome typographical errors ', contains fails a little too precife 



* P. 414, at the end of the firft line, add ai'jmiix; fame page, at the. 

 beginning of the nth line, for/fc;; lead ion; ntitt line, ibi'annfati read' 

 arceau. 



perhaps^ 



