64 SEC170N PHYSICS. 



that heard it. Ponies and cattle, too, are sometimes able to hear very 

 high notes much more than horses ; I once frightened a pony with 

 one of these whistles in the middle of a large field. I can produce no 

 effect on ants, nor on the great majority of insects, though there are 

 some apparent exceptions about which, however. I am not yet prepared 

 to speak. 



The CHAIRMAN : I am sure I need not ask you to thank Mr. Galton 

 for his very interesting remarks. Time is getting on, and I will now 

 invite those who have anything to say upon the general subject of 

 Just Intonation and the Limits of Audible Sound to do so. There was 

 only one remark which occurred to me specially during Dr. Stone's 

 last communication, and that was the able way in which he pointed 

 out the bearing which the mass of the air which is set in motion has 

 upon audibility. It has nothing to do with wave-length or wave 

 amplitude but with the quantity of air, which you may compare to the 

 end-length of sea waves. That seems to have great power and effect 

 on the auditory nerves. Perhaps the lowest audible note which we 

 have heard, at least, is that which you hear when you are outside a 

 tunnel, and you hear the actual throbbing of the piston of the engine. 

 You have an immense mass of air in the tunnel set in vibration. It 

 has nothing whatever to do with the length of the tunnel ; it does not 

 act as an organ pipe establishing stationary waves, but you have an 

 immense mass of air set in deliberate motion with slower vibrations even 

 than sixteen in a second, and the sound is perfectly audible. 



Mr. ALEX. J. ELLIS, F.R.S. : I only wish to say a few words with 

 regard to the experiment of Helmholtz which was alluded to, for trying 

 to determine the lowest limit of tone. His object in operating on a 

 piano string loaded with a kreutzer was to render the upper partials 

 inharmonic to the fundamental, so that he should be quite sure that 

 he heard a simple pendular vibration. His object was to determine 

 the lowest audible limits of such vibrations. The subject is one which 

 has been very recently investigated, and accounts of the experiments 

 have been given by Professor Preyer, of Jena, one of the members of 

 the general committee. There are the pipes here which he experi- 

 mented upon. He found that the best way to hear these sounds, was 

 to obtain them first from a reed attached to a pipe, and then to shut oft 

 the air, and listen to the tone as it vanished, when he heard the funda- 



