NATURAL PHILOSOPHY. 167 



note ; introducing it into a tube 6 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 

 15 feet long, the sound assumes extraordinary intensity. The 

 vibrations which produce it are sufficiently powerful to shake the 

 pillars, floors, seats, gallery, and the 500 or 600 people who 

 occupy the seats and gallery. The flame is sometimes extin- 

 guished by its own violence, and ends its peal by an explosion as 

 loud as a pistol-shot. The vibrations consist of a series of partial 

 extinctions and revivals of the flame. The singing flame appears 

 continuous; but if 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. 



" A flame may be employed to detect sonorous vibrations in air. 

 Thus, in front of this resonant case, which supports a large and 

 powerful tuning-fork, I move this bright gas flame to and fro. A 

 continuous band of light is produced, slightly indented through 

 the friction of the air. The fork is now sounded, and instantly 

 this band breaks up into a series of distinct images of the flame. 

 In this glass tube 14 inches long, a flame is sounding; I 

 bring the flat flame of a fish-tail burner over the tube, the broad 

 side of the flame being at right angles to the axis of the tube. 

 The fish-tail flame instantly emits a musical note of the same pitch 

 as that of the singing flame, but of different quality. Its sound 

 is, in fact, that of a membrane, the part of which it here plays. 

 Against a broad bat's- wing flame I allow a sheet of air, issuing 

 from a thin slit, to impinge. A musical note is the consequence. 

 The pitch of the note depends on the distance of the slit from the 

 flame. 



** Before you now burns a bright flame from a fish-tail burner. 

 I may shout, clap my hands, sound a whistle, or strike an anvil ; 

 the flame remains steady and without response. I urge against 

 the broad face of the flame a stream of air from the blow-pipe. 

 The flame is cut in two by the stream of air. It flutters slightly, 

 and now when the whistle is sounded the flame instantly starts. 

 A knock on the table causes the two half-flames to unite and form 

 for an instant a flame of the ordinary shape. By a slight varia- 

 tion of the experiment, the two side-flames disappear when the 

 whistle is sounded, and a central tongue of flame is thrust forth in 

 their stead. Passing from a fish-tail to a bat's-wing burner, I ob- 

 tain this broad, steady flame. It is quite insensible to the loudest 

 sound which would be tolerable here. I turn on more gas; the 

 flame enlarges, but it is still insensible to sound. I enlarge it still 

 more ; and now a slight flutter of its edge answers to the sound of 

 the whistle. Turning on a little more gas, and sounding again, 

 the jumping of the flame is still more distinct. Finally, I turn on 

 gas until the flame is on the point of roaring as flames do when 

 the pressure is too great. I now sound my whistle ; the flame 

 roars and thrusts suddenly upwards eightlong, quivering tongues. 

 I strike this distant anvil with a hammer; the flame instantly re- 

 sponds by thrusting forth its tongues. Another flame is 18 inches 



