IlS Oji the Longitudhial Vlhrations, &c. 



end of which is fufpended a large filver fpoon, and beats it 

 againft any thing, he will hear a noife, even if his ears are 

 fiuit, equal to that of a large bell. Perolle has given excel- 

 lent obfervations on the capability of hard bodies to conduct 

 found, in the Memoirs of the Academy of Turin for 1790 

 and 1 791. Aniculaied tones alfo are conduced exceedingly, 

 well through hard bodies, as I found by experiments which 

 I made with fome of my friends. Two perfons who had 

 flopped their ears could converfe with each other when they 

 held a long ftick, or a fcries of flicks, between their teeth, 

 or refted their teeth againft them. It is all the fame whether 

 the perfon who fpeaks refts the ftick againft his throat or hi^ 

 breaft, or when one refts the ftick which he holds in his 

 teeth againft fome velTcl into which the other fpeaks. The 

 ePic6t will be greater the more the veflcl is capable of a tre- 

 mulous movement. It appeared to be ftrongeft with glafa 

 and porcelain veflels ; with copper kettles, wooden boxes, 

 and earthen pots, it was weaker. Sticks of glafs and next 

 fir-wood conducted the found beft. The found could alfo 

 be heard when a thread was held between the teeth by both, 



this valuaWe fenfe, which, as Bonnet fays, connefls us with the moral 

 vorld ; for he foot) learned, by means of a piece of hard wood, one end of 

 Avhich he placed againft his tjtth, while another perfon placed the other end 

 in the like manner, to keep up a converfation, and to be able to underfland 

 the leaft whifper. His fon made this beneficial difcovery the fubjed of aa 

 inaugural differtation under the following title : « Dijfrhuio mcdica fijlais. 

 710-iit mcib'jdi furdcs reddaun aiuUsnics phv/lcas el med'uas vatloncs. Pra;f. 

 Andr. El. Buc;inero; aud. Jo.Jorissen. Hala-, 1757.4. One 

 hears moft diftindiy when the end of the ftick refts againft the upper 

 fore-teeth, or rather when it is held between the teeth : if placed only 

 againft the lower teeth, it will be of no avail. The natural caufes of this 

 and many other variations which the author and his father tried, are ex- 

 plained in the above ufeful Traift, which was afterwards publifncd in Ger- 

 nia,n, by the prefuient, with the title of, Bu.:b>ias Ahbandlung 'von (titer 

 hejomkm und Uichten art TauU tiund lu Muckfn : Nebji andan Anmer- 

 iungeyi. ire Samml. Ilalle 1759. S,— [This note is by Profcflcr Biutnen- 

 bach. Edit.] 



ib 



