154 LECTURES TO SCIENCE TEACHERS. 



so on. Here are others arranged for all sounds. Even as I 

 am speaking, if you take a few and try them, you will hear 

 as I fall on the particular note in the inflexions of speech 

 the tube reinforces it. The human voice is very full of 

 harmonics, and if I sing the low C different persons holding 

 these resonators will hear the upper partial notes that I 

 unconsciously produce at the same time as the grave note 

 that I am consciously singing. In this way Helmholtz 

 accomplished that wonderful feat of analysing the tones of 

 different instruments and showing what musical quality 

 depends upon, a fact which was never appreciated or under- 

 stood before. 



Now I have to speak of distributors. These are mentioned 

 by Clerk-Maxwell as air, wood, and metal. The third form, 

 the metal, has lately been revived in a very pretty toy which 

 is being sold about the streets, and is called a telegraph. It 

 is merely a couple of resonators made of pill-boxes or little 

 boxes of tin, with a wire-thread passing between them. Any 

 words spoken into one of these are perfectly audible at the 

 other end. The first mode of distribution by means of air 

 hardly needs much said about it, because it is happening at 

 the present moment as I am speaking to you. 



The second deserves a little illustration ; the more so as it 

 was studied by an illustrious man lately dead, Sir Charles 

 Wheatstone. We have the original mechanism here by which 

 he performed the experiment. This curious, classical-lyre- 

 looking thing is the instrument he used in his form of the 

 telephone. His distributors were simply bars of light deal. 

 I have constructed a long bar of the kind with four pan- 

 tile laths, along the side of the room, and I find even in 

 this considerable length they convey the sound of a tuning- 

 fork to this resonator very well. I will ask my assistant to 

 strike the fork in the air and you will not hear it at all, but 

 when he applies it to one end of the wooden rod, and I apply 

 the other end to this resonator, you all hear it distinctly. 

 The lyre down here is speaking the note produced at the top 

 of the room. More than this, tactile sensation, as I have always 

 contended, is shown to be continuous- with aural sensation, 

 for if I take hold of this rod while the tuning-fork is sounding, 

 I can not only hear the vibration but I can feel it perfectly 

 well at the same time ; thus it is sensible to my auditory and 

 tactile nerves transmitted through the length of wood. It is 



