94 Prof. Tyndall on Sounding and Sensitive Flames. 



length and width, the current of air passing over the flame pro- 

 duces such a flutter, which the resonance of the tube exalts to a 

 musical sound. 



Introducing a gas-flame into this tin tube three feet long, we 

 obtain a rich musical note ; introducing it into a tube six feet 

 long, we obtain a note an octave deeper — the pitch of the note 

 depending on the length of the tube. Introducing the flame 

 into this third tube, which is fifteen feet long, the sound as- 

 sumes extraordinary intensity. The vibrations which produce 

 it are sufficiently powerful to shake the pillars, floor, seats, gal- 

 lery, and the five or six hundred people who occupy the seats 

 and gallery. The flame is sometimes extinguished by its own 

 violence, and ends its peal by an explosion as loud as a pistol- 

 shot. 



The roar of a flaine in a chimney is of this character : it is a 

 rude attempt at music. 



By varying the size of the flame, these tubes may be caused 

 to emit their harmonic sounds. 



Passing from large pipes to small ones, we obtain a series of 

 musical notes, which rise in pitch as the tube diminishes in 

 length. This flame, surrounded by a tube 17 J- inches long, 

 vibrates 459 times in a second, while that contained in this 

 tube, 10| inches long, vibrates 717 times in a second. Owing 

 to the intense heat of the sounding column, these numbers are 

 greater than those corresponding to organ-pipes of the same 

 lengths sounding in air. 



The vibrations of the flame consist of a series of partial ex- 

 tinctions and revivals of the flame. 



The singing flame appears continuous; but if the head be 

 moved to and fro, or if an opera- glass, directed to the flame, be 

 caused to move to and fro, or if, after the method of Wheat- 

 stone, the flame be regarded in a mirror which is caused to rotate, 

 the images due to the revivals of the flame are separated from 

 each other, and form a chain of flames of great beauty. 



With a longer tube and larger flame, by means of a concave 

 mirror, I can project this chain of flames upon a screen. I first 

 clasp my hand round the end of the tube so as to prevent the cur- 

 rent of air which causes the flutter from passing over the flame ; 

 the image of the flame is now steady upon the screen before 

 you. I move the mirror, and you have this continuous luminous 

 band : I withdraw my hand ; the current of air passes over the 

 flame, and instantly the band breaks up into a chain of images. 



A position can be chosen in the tube at which the flame 

 bursts spontaneously into song. A position may also be chosen 

 where the flame is silent, but at which, if it could only be 

 started, it would continue to sound.. It is possible to start 



