166 
POPULAR SCIENCE REVIEW. 
from the burner, will change its shape, and take precisely the 
appearance it has when influenced by sound. Now, the sono- 
rous pulses, excited by a sound, throw the pipe which conveys 
the gas to the burner into vibration, the flow of gas is thereby 
urged from the sides towards the centre of the tube, and, being 
confined within narrower limits, issues from the burner with an 
increased velocity, so long as the sound continues. This, I 
believe, is the simple philosophy of how sonorous vibrations 
can effect an increase in the pressure of the gas ; and, it needs 
but a little reflection, to see the ready explanation it affords to 
every difficulty, e. g., the importance of freedom in the gas- 
passages, the superior effect of high notes, and the fact that 
the nearer the gas is to the point at which its velocity through 
the burner will cause an alteration in the shape of the flame, 
the less sustained and the less loud need be the sound which 
precipitates this change. 
March 20 th. 
