Experiments on. Sound. 245 



in an equal volume of vapour. The author then makes va- 

 rious applications of thefe principles, but particularly to 

 fteam-engines, the diflferent degrees, of the power of which 

 he determines according to the ftate of compreffion of the 

 aqueous vapour. 



Perolle has made experiments on the intenfity of found ia 

 different gafes, Which feem to give a refult contrary to thofe 

 of Prieftley, Chladni, and Jacquin jun. Maunoir and Paul, 

 of Geneva, having infpired hydrogen gas without being in- 

 commoded by it, were much furprifed, when they attempted 

 to fpeak, to find that their voice had become flirill and 

 fqueaking. 



Perolle has given experiments alfo refpefting the propaga- 

 tion of found, by which he fhows that air is not the beft 

 medium for conveying it. He flopped his ears with bits of 

 chewed paper, and, having applied his watch to them, could 

 not hear the noife of its beating. He removed the watch, and 

 placed it in conta<Sl with a fmall cylindric piece of wood, the 

 other extremity of which touched one of thofe external parts 

 of the head that propagate found; fuch, for example, as the 

 cartilaginous parts of the ear; and he then heard the beating 

 of the watch. 



He fufpended the wateh in the middle of a bocal, and found 

 that the found reached him ; but having filled the bocal with 

 water, the found was much ftronger. The joints of the watch 

 had been luted. He placed the watch on different bodies, 

 fuch as wood, a marble table, &c. and found that the latter 

 tranfmitted the found faintly, while the former tranfmitted 

 it with greater or lefs force. He thence concludes that the 

 found of mufical inftruments, fuch as violins, harps, harpfi- 

 chords, &c. depends on the property which wood has of tranf- 

 mitting founds; and that houfes built of marble or ftone are lefs 

 fonorous, becaufe thtle bodies are worfe conduftors of found. 



Lamarck has obferved that founds are tranfmitted in vacuo 

 in water, and throusih the moft folid bodies. The cannon 

 of Toulon are heard at Monaco, that is to fay, at the diflance 

 of more than 25 leagues, while one is lying on the ground ; 

 but the fame founds are not propagated nearly fo far in the 

 air. From this he concludes : 



I ft:, That 



