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Prof, Barton and Dr. Browni 



ino- on 



The lengths of the twenty-five responders (RI II... III. .S) 



range from one to sixteen, and are in geometrical progression. 

 The distances from A of their suspension points are pro- 

 portional to their lengths, so as to ensure that each shall 

 receive an equal forcing from the driver. The advantage of 

 this geometrical progression of length lies in the fact that 

 the " intervals " (to use the musical expression) between 

 adjacent responders are then all equal. Indeed, the whole 

 set of twenty-five responders forms two octaves of the 



Fig. 1. — Apparatus for Harmonic Analysis. 



chromatic scale. It is to be noticed that these light vibra- 

 tional responders have virtual lengths from their bobs to the 

 cord AC and not to AEB. Their bobs consist of paper cones, 

 with the addition of a ring of copper to diminish the damping 

 to a suitable extent, and so make the resonance or response 

 just sharp enough. The bobs were made precisely alike, and 

 this ensured the damping being the same for each responder. 



When first the bob D was allowed to swing freely, only 

 one resonance maximum occurred in the vibration of the 

 responders at the part marked 1 1 in the diagram, thus 

 showing that the motion was simple harmonic of the 

 frequency thus indicated. 



Next, the bob D was moved by hand in a compound 

 harmonic motion of the same fundamental frequency as was 

 natural to it. Then the responders showed the fundamental 



