302 Mr. Challis on the llieory of the 



vincing manner, that when any note n of the series i, 2, 3, &c. 

 is sounded, all the n — i lower notes are heard with it. This 

 also our theory would lead us to expect, inasmuch as it ascribes 

 the sounding' of any note to the prominence of the coefficient 

 of the term corresiJonding to it above those of the other terms. 

 Admitting therefore, as a matter of experience which we have 

 not sufficient data to account for theoretically, that X is always 

 equal to the length of the tube, theory is sufficiently accordant 

 with fact. 



The above theory does not require us to know the precise 

 mode of disturbance, in order to account for the series of notes. 

 I will, however, venture to suggest that when a musical sound is 

 caused by blowing over the orifice of a tube, the disturbance 

 is created by the contiguity of a stratum of air in motion, and 

 therefore, as would appear from Art. 11., condensed or rarefied, 

 to the stratum of air kept at rest by the sides of the orifice, 

 and therefore of mean density. As the condensation is pro- 

 portional to the velocity, a large and slow current would produce 

 a grave note, a small and rapid one, a high note. 



With respect to the tube closed at one end, we may at once 

 infer from what has been said in Art. 12., that its fundamental 

 note, and all its other notes are the same as those of a tube 

 open at both ends of double the length, if the disturbances be 

 made in the two cases under the same circumstances. But till 

 we know every thing that is concerned in producing the vibra- 

 tions in the two tubes, we cannot pronounce with certainty when 

 this identity of circumstance exists. It would seem that the 

 density of the fluid at the open end of the stop-tube must be 

 the mean, and consequently that this must be the position of 

 a loop. The series of notes will therefore be 1, 3, 5, &c. 



There is reason to think that the vibration of the tube itself, 

 is an element entering into the determination of x, for it has 



