H. V. Gill — Theory of Singing Flames. 177 



Akt. XX. — The Theory of Singing Flames ; by H. V. 



Gill, S. J. 



The phenomenon of a jet of gas burning inside an open tube, 

 emitting a musical note, is one of those facts which, although 

 known for very many years and although much written about, 

 have never been fully explained. It is not our intention to go 

 into historical details on the subject, but a glance at the chief 

 explanations which have been proposed will be interesting. 

 De la Kive supposed the sound to be due to a periodic conden- 

 sation of the water vapor produced in the combustion of hydro- 

 gen gas. Faraday showed this theory to be false by the fact' 

 that he obtained a musical note by means of another gas which 

 does not form water as a product of combustion. Faraday 

 explained the sound as being produced by successive explosions 

 of quantities of an explosive mixture of gas and air which suc- 

 ceed each other at certain intervals. Tyndall accepted this 

 explanation. Another theory which has been proposed is that 

 the sound is produced by vibrations maintained by heat, the 

 heat being communicated periodically to the mass of air con- 

 fined in the sounding tube, at a place where in the course of 

 vibration the pressure changes. This explanation, although it 

 takes into consideration the extinction of the flame at periodic 

 intervals by the changes of pressure, is not satisfying, and 

 indeed this very intermittent character of the flame presents 

 in this theory certain serious difficulties. 



Sondhauss performed a series of experiments in which he 

 made use of a flame of hydrogen issuing from a gas-generating 

 flask. His chief conclusion was that the condition of the 

 column of gas in the supply-tube had an important influence 

 on the phenomenon ; for example, if the supply-tube be 

 plugged near the jet with some wool the flame will not sing, 

 though in appearance it is the same as a flame that will sing. 

 This result is a proof that it is impossible to explain the sing- 

 ing by considering merely its effect in heating the air, as in 

 the case of a wire gauze which has been heated. Rijke was 

 able to produce a continuous musical note by means of a wire 

 gauze placed in a tube and kept heated by means of a strong 

 electric current. JSTow if the note produced by a gas flame 

 were owing to the same cause, the flame, even when the 

 supply-tube was plugged, ought to produce a note if placed at 

 the same position as was the hot gauze when it was sounding, 

 but no such result is observed even when the tube is narrow. 



