Prof. Tyndall on Sounding and Sensitive Flames. 93 



investigated by Count Schaffgotsch and myself. The jumping 

 of a naked fish-tail flame, in response to musical sounds, was first 

 noticed by Professor Leconte at a musical party in the United 

 States. He made the important observation that the flame did 

 not jump until it was near flaring. That his discovery was not 

 further followed up by this learned investigator was probably due 

 to too great a stretch of courtesy on his part towards myself*. 

 Last year, while preparing the experiments for one of my "Juve- 

 nile Lectures," my late assistant, Mr. Barrett, observed the 

 effect independently; and he afterwards succeeded in illustrating 

 it by some very striking experiments. With a view to the present 

 discourse, and also to the requirements of a forthcoming work on 

 sound, the subject of sounding and sensitive flames has been re- 

 cently submitted to examination in the laboratory of the Royal 

 Institution. The principal results of the inquiry are embodied 

 in the following abstract. 



Pass a steadily-burning candle rapidly through the air, you 

 obtain an indented band of light, while an almost musical sound 

 heard at the same time announces the rhythmic character of the 

 motion. If, on the other hand, you blow against a candle-flame, 

 the fluttering noise produced indicates a rhythmic action. 



When a fluttering of the air is produced at the embouchure 

 of an organ-pipe, the resonance of the pipe reinforces that par- 

 ticular pulse of the flutter whose period of vibration coincides 

 with its own, and raises it to a musical sound. 



When a gas-flame is introduced into an open tube of suitable 



* The observation of Professor Leconte is thus graphically described : — 

 " Soon after the music commenced, I observed that the flame of the burner 

 exhibited pulsations in height which were exactly synchronous w r ith the 

 audible beats. This phenomenon was very striking to every one in the 

 room, and especially so when the strong notes of the violoncello came in. 

 It was exceedingly interesting to observe how perfectly even the trills of 

 this instrument were reflected on the sheet of flame. A deaf man might 

 have seen the harmony. As the evening advanced, and the diminished con- 

 sumption of gas in the city increased the pressure, the phenomenon became 

 more conspicuous. The jumping of the flame gradually increased, became 

 somewhat irregular, and finally it began to flare continuously, emitting 

 the characteristic sound indicating the escape of a greater amount of gas 

 than could be properly consumed. I then ascertained, by experiment, that 

 the phenomenon did not take place unless the discharge of gas was so re- 

 gulated that the flame approximated to flaring. I likewise determined that 

 the effects were not produced by jarring or shaking the floor and walls of 

 the room by means of repeated concussions. Hence it is obvious that 

 the pulsations of the flame were not owing to indirect vibrations propagated 

 through the medium of the walls of the room to the burning apparatus, 

 but must have been produced by the direct influence of aerial sonorous 

 pulses on the burning jet." — Silliman's American Journal for Januarv 

 1858 ; Phil. Mag. for March 1858. 



