4>76 Prof. Tyndall on the Sounds produced by 



the flame, when the former is sounded and brought near the 

 flame, the jumpings are seen at exactly the same intervals as 

 those in which the beats are heard. When the tuning-fork is 

 brought over a resonant jar or bottle, the beats may be heard 

 and the jumpings seen by a thousand people at once. By chan- 

 ging the load upon the tuning-fork, or by slightly altering the size 

 of the flame, the quickness with which the beats succeed each 

 other may be changed, but in all cases the jumpings address the 

 eye at the same moment that the beats address the ear. 



" With the tuning-fork I have obtained the same results as with 

 the voice and syrene. Holding a fork over a tube which responds 

 to it, and which contains within it a silent flame of gas, the 

 latter immediately starts into song. I have obtained this result 

 with a series of tubes varying from 10^ to 29 inches in length. 

 The following experiment could be made. A series of tubes 

 capable of producing the notes of the gamut, might be placed 

 over suitable jets of gas ; all being silent let the gamut be run 

 over by a musician with an instrument sufliciently powerful, 

 placed at a distance of twenty or thirty yards. At the sound of 

 each particular note, the gas-jet contained in the corresponding 

 tube would instantly start into song. 



I must remark, however, that with the jet which I have used, 

 the experiment is most easily made with a tube about 11 or 12 

 inches long : with longer tubes it is more difficult to prevent 

 the flame from singing spontaneously, that is, without external 

 excitation. 



• The principal point to be attended to is this. With a tube, say of 

 12 inches in length, the flame requires to occupy a certain position 

 in the tube in order that it shall sing with a maximum intensity. 

 Let the tube be raised so that the flame may penetrate it to a less 

 extent ; the energy of the sound w ill be thereby diminished, and 

 a point (A) will at length be attained where it will cease alto- 

 gether. Above this point, for a certain distance, the flame may 

 be caused to burn tranquilly and silently for any length of time, 

 but when excited by the voice it will sing. 



When the flame is too near the point (A), on being excited by 

 the voice or by a tuning-fork, it will respond for a short time, 

 and then cease. A little above the point where this cessation 

 occurs, the flame burns tranquilly, if unexcited, but if once 

 caused to sing it will continue to sing. With such a flame, which 

 is not too sensitive to external impressions, I have been able to 

 reverse the effect hitherto described, and to stop the song at 

 pleasure by the sound of my voice, or by a tuning-fork, with- 

 out quenching the flame itself. Such a flame I find may be 

 made to obey the word of command, and to sing or cease to sing, 

 as the experimenter pleases. 



