Tuies rendered harmonious ly Hydrogen Gas. 5^5 



Let us nnvv examine what takes place in this experiment. 

 There mull be a certain point, which may be calleil the y6- 

 rorons iooit; a U at this point that the vibrations which 

 c MiunaHicaie to the air an undulatory niotio'.i are produced, 

 'i'hls poiiit is the- place of combiii'ion : for by thang.ng the 

 poiuion of thai place the founds mav be varied, as M. Pitlet 

 pruved by a feries of experiments. This gentleman obfcrved 

 aifo in that point, bv mt.in'? of the i'nioke with which he 

 fi'led the tube, a continual fucceffion of vihrations. Thefeyi- 

 brationi^ give birth touiii^ulations, which are propagated with 

 a knovn and determined velocity, anJ. Unking the fides of 

 the tube, arc reflected with the ianic velocity as that with 

 whi(:h they reached them. When the dillance of the fides of 

 the tube is Inch that the reflexions backwards and forwards 

 are ifochronous with the vibrations natural to the fonorous 

 caute, the found incrcafes in intenfity, and becomes mufi- 

 ciiily appreciable. It appears alio that the refleftcd undula- 

 tions re-acl on the primitive vibrations produced in the place 

 of combuftion, and render them harmt-nically regular with 

 them ; lor a certain fpace of time is alnioft always neceflary 

 before the inflrumcnt has acquired a regular and full found : 

 the tone of the tube will be higher or lower according lo the 

 pfreater or lefs number of undulations which take place in a 

 given time. 



There is another eflfential fa6l to be obfervcd in the expe- 

 riment which we here examine : the temperature of the co- 

 lumn of air is not the lame throughout its whole length. At 

 the fonorous point, that is to fay, the place of conibuflion, 

 the ii-mpcrature is exceedingly high ; it is fuch, that the ex- 

 tremity of the aperture of the glafs through which the hy- 

 drogen eras iiTues is conftantly in a flate of incandcfcence: 

 if an inflamed jet of the vapour of fpirit of wine or ether be 

 fubftituted for a current of hydrogen gas, the heat is viflbly 

 weaker. According to fome experiments it appears pr(ibable 

 alfo that the temperature of the chamber where the experi- 

 ment iS made, and the purity of the air in the chamber, may 

 have fome influence on the rcfiilt. 



The objeft of my refearches was lo difcover \h(f caufe of 

 thefc phsenomena, and how, and by what means, tiiefe fono- 

 rou*^ vibrations arc produced. During the con^bullion of hy- 

 dro:iCii gas, it is well kiiown that there is a procivtAion of 

 waier, and this water appears under the form of vapours. 

 The place of the coinbuition being at a li;gh leuiperalurc, 

 thefe vnjiours mull acquire a laige volume; but, coming nii- 

 medialelv ijito contatl with air lefs heated, iheir volume muft 

 be rapidly diminifticd. A vacuum therefore uiull be formed. 



