376 



Prof. Tyndall on the Action of Sonorous 



indirect vibrations propagated through the medium of the walls 

 of the room to the burning apparatus, but must have been pro- 

 duced by the direct influence of aerial sonorous pulses on the 

 burning jet" * 



The significant remark that the jumping of the flame was not 

 observed until it was near flaring suggests the means of repeat- 

 ing the experiments of Dr. Leconte ; while a more intimate 

 knowledge of the conditions of success enables us to vary and 

 exalt them in a striking degree. Before you burns a bright 

 candle-flame : I may shout, clap my hands, sound this whistle, 

 strike this anvil with a hammer, or explode a mixture of oxygen 

 and hydrogen : though sonorous waves pass in each case through 

 the air, the candle is absolutely insensible to the sound ; there 

 is no motion of the flame. 



I now urge from this small blowpipe a narrow stream of air 

 through the flame of the candle, producing thereby an incipient 

 flutter, and reducing at the same time the brightness of the 

 flame. When I now sound a whistle the flame jumps visibly. 

 The experiment may be so arranged that, when the whistle 

 sounds, either the flame shall be restored almost to its pristine 

 brightness, or the amount of light it still possesses shall dis- 

 appear. 



The blowpipe-flame of our laboratory is totally unaffected by 



Fig. 1. 



Fie. 2. 



the sound of the whistle as long as no air is urged through it. 

 By properly tempering the force of the blast, I obtain a flame of 

 the shape shown in fig. 1, the blast not being sufficiently pow- 

 erful to urge the whole of the flame forwards. On sounding 

 the whistle the erect portion of the flame drops down, and while 

 it continues to sound we have a flame of the form shown in fig. 2. 

 Here, moreover, is a fish-tail flame, which burns brightly and 



* Phil. Mag. March 1858, p. 235. 



