41)6 



Less conspicuous, but still very dislirict is the resonance reinforce- 

 ment with a number of hearing apparatus I examined some time ago 

 by means of microphone and string-galvanometer and which I have 

 now measured again by Lord Rayleigh's mode of arrangement. 



Reinforcing influence of German apparatus, compared with that of a control- 

 funnel of 21 cm2. 

 (Measurement in the camera silenta). 



Average 



6.4 



11.4 



5.5 



6.7 



