416 Mr. Challis on the general Equations, S^c. 



that as a> just before the stream enters the atmosphere must be 

 greater than w^, p will be less than P, and the pressure will be 

 from without to within. Thus the extreme edge of each la- 

 mina will have a tendency to vibrate simultaneously about 

 two points; one vibration depends on its elasticity, the other 

 on the mode of action of the fluid. The result will be a con- 

 tinual vibration about another fixed point. It is to be observed 

 that the perfect elasticity of the lamina is not a necessary con- 

 dition, and that the action of the fluid is such, that the vibrations 

 would be kept up without intermission, if the vibrating substance 

 were of a yielding nature like leather. It is, I think, by reason 

 of a mode of action of the air, at least similar to that I have 

 attempted to describe, that the general principle stated by Pro- 

 fessor Airy (Caw*. Phil. Trans. Vol. III. Part II. p. 370.) 

 becomes applicable to Mr. Willis's very interesting experiment, 

 illustrative of the mechanism of the vocal organs. 



J. CHALLIS. 



Thinity College, 

 Feb. 20, 1830. 



