Intelligence and Miscellaneous Articles. 411 



litated if, while the string is sounding, the position of the mouth is 

 altered, as if it were wished to say Papa, or the tube is inserted in 

 the mouth when adjusted for A, after the string had been struck. 



The production of resonance by the first partial tone occurs with 

 the piano when the mouth is adjusted for A, in the interval b" to 

 g" , strongly by g u % and a", feebly with g" and b" ; in the octave it 

 is most perceptible at a, its second, and at d' its third partial tone. 

 In the ordinary octave, and in that below the line, the maxima and 

 minima of resonance are more difficult to distinguish. For the 

 lower strings have, without exception, one or more partial tones, 

 which are sufficiently near the special note of the cavity of the 

 mouth to be able to appreciably excite resonance. Hence by 

 strengthening those partial notes they all assume the clang of the 

 vowel A. 



On a second piano I found the maximum of resonance, in accord- 

 ance with the investigations of Von Helmholtz, at b"; and on a 

 third indifferently at a" and b". 



For those who wish to repeat the experiments the clangs of the 

 strings are collated, whose first, second, or the partial tone will 

 excite the maximum resonance, when the special note of the cavity 

 of the mouth agrees with the first note of the series : — 



123456 78 9 10 11 12 



b" b' eTj b g# <$ (-) B G# n (-) D# 



If the special note of the cavity is at a certain interval higher or 

 lower, for instance half a note, the whole pitches of the series are 

 to be raised or lowered by the same interval. 



II. Experiments of this kind may also be easily made with the 

 monochord, when the numbers of vibrations of the partial notes may 

 be directly determined with the aid of a tuning-fork. 



For instance, under a lightly stretched thin steel wire a bridge 

 is pushed from one end until the piece of wire between it and the 

 end I, when twitched in the middle, excites the resonance of the 

 cavity of the mouth most powerfully, which, with a successive pro- 

 longation of the piece of the string struck, occurs with the first 

 partial tone. The limb of a sounding tuning-fork of known num- 

 ber of vibration, s, is then moved over the string from the bridge to 

 the point where, when touched by the rod of the tuning-fork, it 

 puts the portion of the w T ire Z 2 between it and the bridge in co- 

 vibration. From the data l v Z 2 , s, the number of vibrations x of the 

 note of the mouth is obtained, 



h 



Thus in an experiment in which a tuning-fork of 444-5 vibrations 

 was used, 



^ = 185, Z 2 =38-5. 

 Hence 



#= g^ x 444-5=925 (nearly 6"). 

 lo'o 



