MUSICAL SOUNDS PRODUCED BY HIDROGEN GAS. 29 



the period of combuftion is at fo high a temperature, that itExpanfions and 



always ignites the tip of the glafs tube : this hot elaftic vapour, ^ olh P^ Qn ^ of 



at the moment of its production, comes in contact with the cold near the point 0/ 



air, which enters through the bottom of the tube and goes ou t coi nbuftion. 



at the top. Its volume muft be diminiflied the inftant it ftrikes 



this air ; other heated vapours fucceed the former, and are alfo 



contracted : this alternate expanfion and contra6lion_produces 



the undulatory motion of the air, and caufes the fonorous 



waves. 



We have found that an inflamed ftream of alcohol or ether Alcohol and 



produced no found in a tube. This is a proof of my obferva-^ s er h g a u t m a ^ d itl1 



tion, that in order to produce found, there muft be a great dif- produce elaftic 



ference in the temperature of the vapour and the ambient air. flu . ld whlch {* 

 . -ii r • neither rapidly 



There is certainly, in this cafe, a formation of vapours and fuc- nor totally con- 



ceffivecondenfations, for the water runs along the fides of the denfcd * 

 tube ; but the point of combuftion is infinitely lefs hot than that 

 of hidrogen, confequently the vapour produced is much lefs 

 heated and elaftic. This cafe is limilar to that formerly men- 

 tioned, where it was (hewn that vaporization and fucceffive 

 condenfation of the liquid might be effected without fonorous 

 undulation, merely by expofing the bulb to a certain degree of 

 heat not intenfe enough for this laft purpofe. We cannot be Why there is 

 furprifed that there is lefs heat produced by the combuftion of lefs hear * 

 alcohol or ether than by that of hidrogen, if we confider, that 

 in the latter cafe all the caloric contained in the gas and the at- 

 mofpheric oxigen which is confumed, becomes fenfible heat, 

 ahd is paffed totally into the vapour produced. On the con- 

 trary, in the combuftion of an inflammable fubftance, fuch as 

 alcohol, the caloric of the oxigen confumed alone becomes 

 fenfible, and this alfo is moftly abforbed by the production of 

 carbonic acid gas ; fo that the excefs alone paffes into the va<- 

 pour. It is not therefore furpriiing that the heat is not fum% 

 cient to give the vapour elafticity fufficient to produce founds. 

 The prefence of carbonic acid gas, which is one of the refults 

 of the combuftion, may alfo prevent the fonorous vibrations. % 



The found is much ftronger in the tubes with hidrogen, than The found by 

 in thofe with bulbs. It is likewife more permanent ; for the nidr0 S enis 

 tube being open at both ends, a current of cold air conftantly m^entTbecaufe 

 enters at the bottom and iflues out at the top : this current of the COft &»nt 

 air takes up and carries off the hot elaftic vapours, receives ^produce* the 

 their impulfe, and by attracting a portion of their caloric, di- condenfations 



minifl.es inwfflnt,jr> 



