SENSITIVE FLAMES, ETC. 195 



where the whistling or rustling of the air gives rise to a 

 multitude of sounds, only one of which is strengthened 

 by the resonance of the air within the pipe. In like 

 manner this affords an explanation of the so-called singing 

 flames. Instead of using air urged through a narrow 

 orifice, we have gas urged through a narrow orifice ; 

 which itself produces a slight noise or rustling sound ; 

 and further the combustion of the gas gives rise to a 

 rapid current of air within the tube which is placed 

 over it. The tube around the flame is capable of respond- 

 ing to one note, and only one ; and hence by proper ad- 

 justment of the tube with regard to the flame, the flame 

 will sing or produce a continuous musical note. With 

 a longer tube you hear a lower note produced, owing to 

 the fact that the resonance of this longer tube responds 

 to a note of lower pitch. The tube may be easily tuned 

 to a note of a definite pitch by a paper slider on the end 

 of the tube. Wheatstone has, indeed, made a flame 

 organ on this principle. Here is the instrument from the 

 Loan Exhibition. By depressing the keys of the instru- 

 ment certain gas jets are suddenly thrown within their 

 tubes, and the tubes corresponding to these burners then 

 begin to sing. Thus you can play a few chords upon an 

 instrument of this kind. 



It has long ago been shown how these singing flames could 

 be modified by simply heating a piece of wire gauze which 

 was placed within the tube. If the wire gauze be made 

 red-hot, then a broken current of air passes up the tube. 

 The air passing through the wire gauze thus produces a 

 slight rustling sound in the tube. Out of these notes the 

 tube selects the proper note belonging to itself, and rein- 

 forces that note, and by the resonance of the air in the 

 tube we have a musical sound produced. I will warm the 

 wire gauze by a flame. You will see in this case that 

 when the tube is held horizontally, the current of air and 

 the sound cease, but when the tube is vertical the note re- 

 appears. 



We must pass on to the last fact in this chain of pheno- 

 mena. The body receiving the vibration and accepting it 

 may be in such a peculiar abnormal state that a slight 

 disturbance will produce a great and disproportionate 

 result. And we may term this the sensitive state. 



o 2 



