M. C. Sondhauss on the Refraction of Sound. 



77 



which value is too great. If, however, the exponent of refrac- 



4 

 tion be taken at ^ or 1'333, we obtain 



which coincides with the experiments. 



I will take the liberty of mentioning in conclusion one or two 

 other experiments which I have made with the sound-lens. Words 

 and entire sentences spoken softly by a person standing at one 

 side of the lens were distinctly understood by an observer whose 

 ear was placed at a suitable distance in the axis at the other side ; 

 so that between these two persons a conversation might be held 

 which would be scarcely, if at all, understood by those standing 

 around. I have also made experiments with more intense sono- 

 rous waves, which are likewise refracted and brought to conver- 

 gence by the lens. In the place of the watch a small organ-pipe 

 was fixed, blown through, and its tone at the opposite side of the 

 lens observed. Although the sonorous waves reflected from the 

 walls of the chamber and reaching the ear of the observer exer- 

 cised a disturbing influence, it was shown in the most decided 

 manner that the tone of the pipe behind the lens was much 

 stronger. The ear of the observer, whenever it was brought into 

 the axial line, experienced a regular shock. The tone of the 

 pipe undergoes by its passage through the lens no alteration as 

 regards height and character. 



Later Addition. 



With regard to these experiments on the refraction of sound, I 

 would further remark that I corroborated them afterwards in an 

 objective manner. As source of sound I 

 made use of an organ-pipe, and permitted 

 the waves which were refracted and con- 

 centrated by the sound-lens to act upon 

 the tin tube ahcd. They enter the wide 

 mouth cdj and excite tremors in a fine 

 membrane drawn over ah, which are ex- 

 hibited by the motion of sand strewn upon 

 the membrane. 



