30 Tzibes rendered hartnoTHous ly Hydrogen Gas, 



We have already fcen that an inflamed jet of fpirit of wlnC 

 or of ether cannot make the tube found. This is a new^ 

 proof of what I have advanced, that to produce found there 

 muft be a great difference between the temperature of the 

 vapour and that of the furrounding air. In this cafe there 

 is a fucceffivc formation and condenfation of vapour, for the 

 water (trcams along the fides of the tube ; but the place of 

 combuftion has a much inferior degree of heat to what it has 

 when hydrogen gas is burnt, and confequently the vapour 

 produced has kfs heat as well as Icfs elallicity. This cafe is 

 analogous to that already mentioned, when we faid that afuc- 

 ceflive evaporation and condenfation of the liquid might be 

 produced in a tube having a bulb, without any fonorous ef- 

 ie6ls, by expofing the bulb to a certain degree of heat, but 

 lefs inlenfe than that neceflary for making the tube emit a, 

 found. We fliould not be furprifcd if lefs heat were produced" 

 by the combuflion of fpirit of wine, or ether, than by that of 

 hydrogen gas, when it is confidered that in the latter cafe 

 all the caloric contained in this gas, and in the oxygen of the 

 atmofpheric air confumed, becomes fenfible heat, and miites 

 itfelf entirely with the vapour produced. On the other hand, 

 in the combuftion of an inflammable fubftance, fuch as fpirit 

 of wine, we have only the caloric of the oxygen confumed, 

 rendered fenfible, and which is in a great meafure abforbed 

 by the formation of carbonic acid gas, fo that it is only the 

 excefs which joins the vapour. It is therefore not aftoniiliing 

 that we have not heat fufficient to give to this vapour all the 

 elaft;icity neceflary for the production of found : the prefence 

 of the carbonic acid gas refulting from the combuftion may 

 alfo be an obftacle to the fonorous vibrations. 



In tubes emplcyed with hydrogen gas, the found is much 

 flronger than in*th')fe having bulbs: befides, in the former 

 I', is permanent, in the latter it continues only a few mo- 

 fiictits. The realon of this is as follows : In the apparatus 

 'X.'-.ih hydrogen gar. the tube is open at both extremities, con- 

 fequently thc-re is formed a current of frcfli air, which enters 

 at the boUom and ■ lues at the top ; this current of air fweep- 

 ing; alon{;, with the imt and elaftic vapours receives their im- 

 ^)u]fe, and, by taki:.^ from thcni a portion of caloric, dimi- 

 ziiflics their volum'j: we find here, therefore, the moft cflen- 

 tial condition for ihe crodudlion of an inlenfe and permanent 

 fjund, viz, a gra,^ difference between the temperature of the 

 aiiand thatof the vapour; and this diflcrence always remains 

 the fan.e by the continual renovation of the air; but thi^ 

 iloes not take place in tubes with bulbs, and therefor? tjje 

 found they emit is weaker and of fliorter duration. 



Frona 



