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



Then, knowing the number of beats that the fundamental of the 

 note gives with its corresponding fork, we can designate the 

 number of any other harmonic by the number of beats it makes 

 with a fork of known pitch ; for the number of beats observed, 

 when referred to the number of beats of the fundamental as 

 unity, will be directly as the number of the harmonic in the 

 series. If we cannot well alter the pitch of the composite sound, 

 then it will be well to use forks with sliding weights on gradu- 

 ated prongs, or loaded strings accurately tuned and provided with 

 metre scales. In this system of analysis it is very important to 

 guard against being led astray by the beating of resultant tones ; 

 therefore the forks or strings should be gently vibrated, and 

 resonators used to assist the ear. 



(6) Analysis by means of a loose membrane which receives the 

 composite sonorous wave and transmits its vibrations through 

 filaments or light rods to a series of forks mounted on their 

 resonant cases. 



This method of analysis is the one we devised in our experi- 

 mental confirmation of Fourier's theorem and described in sec- 

 tion 1. We here wish to call attention to the precision of this 

 method of analysis, while at the same time acknowledging the 

 delicate instrumental conditions required to use it successfully. 

 The principal interest attached to it is that it shows in a vivid 

 manner the operation of the instantaneous decomposition of a 

 composite wave into its elementary pendulum-vibrations. The 

 method has also peculiar interest as showing, in the most striking 

 manner, the exaltation of the action of very feeble periodic im- 

 pulses to such degrees of intensity as to set into synchronous 

 vibration very large masses of matter; and it may be well before 

 we discuss the subject proper of this section to call attention to 

 this very interesting result as set forth in the following experi- 

 ment with our apparatus. To the membrane covering the hole 

 in the box of the reed-pipe I attached one end of a fibre of silk- 

 worm cocoon 1 metre long and weighing 1 milligram. The 

 other end of the fibre was cemented to the face of a prong of an 

 Ut 9 fork. This fork weighed 1500 grms., while the top of its 

 resonant box and the air in the latter weighed respectively 102 

 and 22 grms. Therefore the fibre set in motion 1,624,000 times 

 its own weight by only a fraction of the force which traversed it ; 

 and even this force was a yet more minute fraction of the whole 

 energy of the aerial vibrations produced by the reed. 



An experiment like the above is instructive as an analogical 

 illustration of the manner in which we may imagine an setherial 

 vibration to produce chemical decomposition by causing such 



