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



as intense as those of the watch. On the same nights 

 that I made the above determinations I also put the clock on 

 the post, and placing against my zygomatic process a slender 

 stick graduated to inches and tenths, I stood with my ear at 

 distances from the clock of from eight to sixteen feet, and then 

 slid the watch above and along the stick (taking care that it 

 did not touch it) until it reached such a distance from the ear 

 that its fifth tick just disappeared. Knowing the relative in- 

 tensities of the ticks of clock and watch when placed at the 

 same distance from the ear, the law of the reciprocals of the 

 squares gives the relative intensities when the clock and 

 watch are at the several distances obtained in the above ex- 

 periments. Large numbers of such experiments have been 

 made; and the results agree perfectly well when we take into 

 consideration, first, the difficulty thrown in the path of the 

 determinations by the gradual fading away of the watch-ticks 

 as they approach coincidence with the clock-ticks, and 

 secondly, the impossibility of arriving at any result at all if 

 the slightest noise (the rustle of a gentle breeze, the piping of 

 frogs, the bark of a distant dog) should fall on the ear of the 

 observer when engaged in making an experiment. The 

 general result of the numerous experiments thus made shows 

 that the sensation of the watch-tick is obliterated by a coin- 

 cident tick of the clock when the intensity of the clock-tick 

 is three times that of the watch-tick. This result, however, 

 must be regarded as merely approximative, not only from the 

 manner in which it was obtained, but from the complexity of 

 the sounds on which the experiments were made. It is in- 

 teresting, however, both as being, I believe, the first deter- 

 mination of this kind that has ever been made, and as having 

 opened out a new and important field of research in physio- 

 logical acoustics. 



Experiments on the Interference of the Sensations of Musical 

 Sounds. — Reserving the further development of my dis- 

 coveries for future papers, I will now briefly describe some 

 of the more prominent and simple phenomena which I dis- 

 covered in experimenting with musical sounds. At the outset 

 I will remove an objection always made by those versed in 

 acoustics but unacquainted with these new phenomena. It 

 is as follows : — " You say that one sound may obliterate the 

 sensation of another ; but are you sure that the real fact is 

 not an alteration of the quality of the more intense sound by 

 the action of the concurrent feebler vibration ?." I exclude 

 this objection by experimenting as follows: — An open or 

 closed organ- pipe is sounded forcibly; and at a few feet from 

 it is placed the instrument emitting the sound to be oblite- 



