182 



H. V. Gill — Theory of Singing Flames. 



This explanation will be found to account for all the facts 

 which have been observed regarding the singing flame. From 

 it we see that the chief cause to be taken into account is the 

 pressure on the gas, although the flame also plays its part. 



The following facts prove the correctness of this explana- 

 tion. 



We stated that the gas was forced back into the burner dur- 

 ing a condensation, and that it may happen that the flame is 

 forced back with it. With an aperture of such a size (0'5 mm in 

 diameter) as is usually, employed no such result could be 

 observed. With a glass tube drawn to a point having an 

 aperture of about 2 mm diameter, singing inside a tube 70 cm 

 long by 2*5 cm in diameter, we noticed clearly that this result 

 actually took place. The image of this flame as seen in the 

 rotating mirror was like that roughly represented in fig. 3. 



\ WW \ VA V 



This experiment is rather difficult to make, and the note only 

 continues for a short time owing to the size of the aperture. 



The following experiment shows the same thing in a more 

 simple manner. As we have seen, the rapid increase of pres- 

 sure during a condensation in the sounding-tube produces a 

 downward compression on the gas. It ought, therefore, to be 

 possible to detect this by means of a manometric flame. Fig. 4 

 explains itself. 



When the manometric flame is observed in a rotating mirror 

 the ordinary appearance of a Koenig flame is seen, as is repre- 

 sented in the lower part of flg. 5. In this figure the tongues 

 are somewhat exaggerated in distinctness. 



We can use this same arrangement for another interesting 

 experiment. From what we have seen it is clear that the 

 tongues of the image of the manometric flame ought to coincide 

 with the dark spaces of the image of the singing flame, if both 

 images could be perfectly superposed. Since the little shock on 

 the gas is practically transmitted instantaneously throughout the 



