J72 PRODUCTION OF SOUND TN VAPOUR. 



In aqueous va- We then iiitrodticed into the j^lo^^e, in the way I have 



pour sound descrihed, a small nuantit\' of water, part of which was con- 

 produced , . „,, *^ , . , . , , , 

 verted into vapour. 1 he sound immediately began to be 



perceptible, though the density of this vapour was ex- 

 tremely small, the temperature being only ig" [66-2° F.]. 

 proportional To increase it, an excess of water was admitted into the 

 to Its density, gio})^, and it was placed in a stove at the temperature of 

 46° [1I4*8'' F.]. The sound then became very perceptible: 

 it could be heard without stooping down to the globe, and 

 even out of the stove througli the door. Some water still 

 remained in the globe, so there can be no doubt, that the 

 sound was produced and transmitted in the aqueous va- 

 pour. 



When the globe was taken out of the stove, the tempera- 

 ture quickly fell : a great part of the vapour therefore, 

 which had been raised in consequence of the temperature, 

 was necessarily precipitated; and accordingly the sound 

 appeared very evidently diminished. 

 ■In vapour of Without any alteration in the apparatus, we introduced 

 the same quantity of alcohol, as we had before of water. 

 The specific gravity of this alcohol wasO'823. The vapour 

 from this mixture possessed of course greater density and 

 elasticity than that of water at the same temperature; and 

 accordingly the sound was much more perceptible: it wa» 

 heard from one extremity to the other of the rooms that 

 form the philosophical apartnients at Arcueil. Sound 

 therefore is produced and transmitted in the vapour of al- 

 cohol. 

 r.xperimentin As a last experiment we. tried the vapour of ether. This 

 rapourof particularly excited our curiosity, on account of its great 

 elastic force and density, which are known to be very consi- 

 derable ; two circumstances, that rpust contribute to in- 

 crease the intensity of the sound. We begun with drying 

 the globe, because the moisture would have diminished the 



Distance at tension of the ether ; and then allowed the atmospheric air 



vliich the r 1 -11 • - MM • -11 



round was to enter freely, till it was m equilibrio with the external 



Jv-a-^d in at- pressure, which was 0*7613 [?9-951 inch.]; and, carry- 



aifohol sound 

 ♦ouder, 



•iios])heric ai 



ing it into a long walk in the garden, we found, that 

 the sound of the bell was sensible to the distance of 

 J 45 met, [158-5 yd-] : beyond this it wus so faint, that the 



perception 



