372 Scientific Proceedings, Royal Dublin Society. 



calls it — and not to sinuosity. But with this question we cannot 

 here deal. 1 



On the general question of the cause of difference-tones, Lord 

 Kayleigh, though supporting the Helmholtz theory, remarks 

 that "it presupposes a more ready departure from the superposition 

 of vibrations within the ear than would have been expected." 2 

 The experiments with sensitive jets certainly indicate that a more 

 complete theory is required; and it is to be hoped that Lord 

 Eayleigh will be able to give it to us. 



1 The difference between a high-pressure sensitive flame issuing from a pin-hole 

 orifice, and a low-pressure sensitive flame issuing from a nicked ori6ce, is very marked, 

 a definite fish-tail flame being produced by a musical note in the latter case. Possibly 

 the cause of the speaking of the sensitive flame may be analogous to that suggested by 

 Lord Eayleigh as the source of sound in a " bird-call," or small pair of parallel plates, 

 perforated with a central hole through which a current of air is driven. 



2 "Theory of Sound," vol. ii., p. 462. 



