MUSICAL SOUNDS PRODUCED BY HIDROGEN GAS. Q*J 



it will be found that the vapour occupies only a certain part 



of the inftrument, and that air is always prefent. I have fre- Proof of this. 



quently endeavoured to determine the exact fpace occupied 



by the vapour at the moment the found was heard, and I 



found, at Ieaft in the fmall tubes, that it was nearly equal to 



the volume of the bulb. In order to determine this, I clofed 



the orifice of the tube with my finger at the moment it began 



to found ; I then plunged the end of the tube in mercury, 



withdrew my finger, and fufTered the apparatus to cool. The 



vapour thus became condenfed, and the fpace it occupied was 



eftimated by the quantity of mercury which the prefTure of the 



atmofpherecaufed to rife in the tube. 



Such are the four conditions effential to the production of Recapitulation, 

 founds; namely, a bulb at the extremity of the tube; the pre- 

 fence of a very fmall quantity of water or mercury in this bulb ; 

 the application of a ftrong heat to it, whilft the remainder of 

 the tube remains cold ; and, laftly, the fimultaneous prefence 

 of atmofpheric air and vapour in the apparatus ; it is fcarcely 

 negeflary to add, that the orifice of the tube fliould be always 

 open. Let us now confider what may be the caufe of the 

 found. I firft endeavoured to determine whether any chemi- The found is not 

 cal decomposition of the liquid employed took place. For this mkaUh™ c^' 

 purpofe I ufed a tube fufficiently long to permit all the liquid 

 to condenfe in it; I weighed it carefully before I fubjecled it 

 to experiment, and found that its weight was neither aug- 

 mented nor diminithed after repeated productions of found : 

 Whence I conclude, that the caloric has no chemical effect on 

 the liquid, but that it only experiences fucceffive evaporations 

 and condenfations. Muft we then attribute the found to the nor by evapora- 

 evaporation and condenfation of the liquid ? I thought fo at f^ n . dconde,v ' 

 firft, but the following confiderations made me alter my opi- 

 nion : I firft obferved that it was poflible to have a fucceflive fox thefe laft 

 evaporation and condenfation of the liquid, without producing m ? y , *ppea 

 found : this was effected by applying heat not fufficiently in- 

 tenfe to produce found. Secondly, When the experiment was 

 made with a drop of water, I always found that the moment 

 when the apparatus began to found, was that at which the 

 whole fluid had evaporated, and consequently that the caloric 

 acts on the vapour alone. While the fmalleft atom of liquid 

 water remained in the bulb, no found was produced. From 

 this fact I have deduced, that the found is produced by the 



action 



