178 Mr. G. Johnstone Stoney • [Feb. 6, 



WEEKLY EVENING MEETING, 



Friday, February 6, 1885. 



Sir Frederick Beam well, F.R.S. Manager and Vice-President, 

 in the Chair. 



G. Johnstone Stoney, Esq. M.A. D.So. F.R.S. 



How Thought presents itself in Nature. 



All the main steps in the great progress which man has been able to 

 make in understanding the universe in which we live and of which 

 we form a part have consisted in ascertaining that there is more 

 simi^licity in what occurs than had before been known to prevail. It 

 is the aim of the present discourse to endeavour to follow this 

 simplification up to the stage to which scientific inquiry has now 

 succeeded in carrying it, and to point out a further simplification, 

 which is suggested and rendered probable by that which has been 

 thus ascertained, although we are not yet in a position to speak con- 

 fidently about this further step. 



Sound is Motion. 



A very important discovery was made when it was found that 

 while we are listening to sound what is really occurring in the outer 

 world is merely a motion of materials all of which were there before. 

 Thus in playing a piano the strings are made to vibrate by the per- 

 former ; this sets up a quivering motion in the sounding-board 

 corresponding to the motion of the strings, and the sounding-board 

 in its turn transmits an undulation through the air, some very small 

 part of which occurs within the outer passage of our ear. It here 

 encounters the membrane which separates the outer from the middle 

 chamber of the ear, and through it communicates the motion to the 

 air of the middle chamber and to three delicate little bones which 

 finally carry the motion forward to the inner chamber where the 

 true auditory apparatus suspended in a liquid is operated upon by 

 the vibratory motion, and in its turn acts upon the multitudinous 

 filaments of the elaborate fringe in which our nerve of hearing 

 terminates. 



The whole of the phenomenon then so far as it exists in the 

 outer world consists entirely of motions, and it becomes sound only 

 at Some stage beyond the portals of our ears. \\'hen this was found 

 out, a very important discovery was made respecting the actual 

 operations of nature. This discovery was followed up by investiga- 

 tions, through which a multitude of details have been brought to 

 light, as, for example, that the pitch of the sound as we hear it 



