Prof. A. M. Mayer's Researches in Acoustics. 503 



rated, which may be either a tuning-fork on its resonance- 

 box or a closed organ-pipe communicating with a separate 

 bellows. Suppose that in the following experiment both 

 tuning-fork and closed organ-pipe produce a note higher in 

 pitch than the more intense or extinguishing sound of the 

 open organ-pipe. Now sound the fork alone strongly, and 

 alternately shut and open its resonance box with the hand. 

 We can thus obtain the sound of the fork in a regular measure 

 of time. When the ear has well apprehended the intervals of 

 silence and of sound thus produced, begin the experiment by 

 sounding the open pipe and tuning-fork simultaneously. 

 Now if any change is thus effected in the quality of sound 

 emitted by the open pipe, this change cannot occur except 

 when the fork is sounded, and hence, if it occurs at all, it 

 must occur in the regular measure in which the fork is 

 sounded. The following are the facts really observed. At 

 first every time that the mouth of the box is open the sound 

 of the fork is distinctly heard and changes the quality of the 

 note of the open pipe. But as the vibrations of the fork run 

 down in amplitude the sensations of its effect become less and 

 less till they soon entirely vanish, and not the slightest change 

 can be observed in the quality or intensity of the note of the 

 open organ-pipe, whether the resonance box of the fork be 

 open or closed. Indeed at this stage of the experiment the 

 vibrations of the fork may be suddenly and totally stopped 

 without the ear being able to detect the fact. But if instead 

 of stopping the fork when it becomes inaudible we stop the 

 sound of the open organ pipe, it is impossible not to feel sur- 

 prised at the strong sound of the fork which the open pipe 

 had smothered and had rendered powerless to affect the ear. 

 If we replace the tuning-fork by a closed organ-pipe of the 

 same pitch, the results will be the same ; but in this case I 

 adjust the intensity of the higher closed pipe to the point of 

 extinction by regulating the flow of air from the bellows by 

 a valve worked with a screw. The alternation of sound 

 and silence is obtained by closing and opening the mouth 

 of the closed pipe by the hand. 



2. On the Discovery of the Fact that a Sound, even when intense, 

 cannot obliterate the sensation of another Sound lower than it 

 in pitch. 



High Sounds cannot obliterate Low Sounds. — A new and 

 remarkable fact was now discovered. No sound, even when 

 very intense, can diminish or obliterate the sensation of a 

 concurrent sound which is lower in pitch. This was proved 

 by experiments similar to the last, but differing in having the 



