144 LECTUEES TO SCIENCE TEACHEE8. 



the transverse direction to the string. Here again we have 

 the same composition of harmonic motions which I have 

 already shown you, one instrument deflecting the ray laterally 

 and the other vertically \ so you get regular figures, which 

 become steady when unison or concord is going on, but which 

 flicker into innumerable changing lines when dissonance is 

 present. In this way he was enabled to analyse the vibrations 

 of a violin string in motion, and remarked that regular figures, 

 free from jumps, starts, and abrupt changes smooth vibra- 

 tions, in fact, such as you saw just now were more easily 

 obtained from fine old instruments than from raw modern 

 fiddles. This is very curious, because it has always been a 

 great question of doubt and difficulty why old violins pro- 

 duce a so much finer tone than modern ones. I have endea- 

 voured myself to utilize this observation of Helmholtz by 

 rendering the sound-board of the fiddle more homogeneous. 

 Here is an instrument to which the contrivance is applied so 

 as to get the sound transmitted more nearly like that of a 

 fine old instrument. I cannot go fully into the question of 

 tension bars, but I find better effect is produced by putting 

 strengthening bars along the belly of the fiddle, so as to make 

 it more homogeneous without adding materially to its weight. 

 Helmholtz also found that the interior of an old fiddle adds 

 resonance by the body of wind it contains ; I have here an 

 old violin, and an old tenor ; if we blow into the body as into 

 a wind-chest we can repeat his observation ; we can use it, in 

 fact, as a sort of whistle or organ-pipe ; of course it gives a 

 rough note, but still you can hear the pitch of it. The tenor 

 is rather clearer, and there is quite the difference of a tone 

 between the two. The result of Helmholtz's experience was 

 that a Straduarius violin gives C, tenors a note lower, and 

 violoncellos generally give F, or G, in the bass. 



I proceed next to speak of rods, bars, and tuning-forks, 

 which are only exceptionally used in artistic music ; although 

 there is an instrument employed by Mozart in the Flauto 

 Magico to imitate the sistrum, with which Papagino is sup- 

 posed to be gifted, consisting of metal bars which strike a 

 scale of high notes it is called a glockenspiel. This is only 

 an exceptional case to produce a particular effect, but I can 

 show you the character of such notes by means of a steel bar. 

 If I take this bar of cast steel and strike it on one end, you 

 hear first of all rather faintly the fundamental note such as I 



