252 Mr. Willis on the Vowel Sounds, 



The note always increases in loudness on approaching/, and 

 diminishes when it begins to flatten. After the leap it is com- 

 monly husky and bad for a little distance, and at every point c, 

 that is, whenever the pipe is a multiple of the whole wave of 

 the reed, the tone of the reed appears to be perfectly unaffected 

 by the pipe, and is, if any thing, rather less loud than it would 

 be without it. 



Similar ])henomeiia have been imperfectly observed by the 

 old organ builders, and have been described by Robison, who 

 set a reed in a glass foot, and adapted a sliding telescope tube 

 to it. Again by Biot, who also used a glass foot, but made the 

 length of the reed to vary instead of that of the pipe*. All these 

 experiments were made however with the old-fashioned reed, 

 whose oscillations were disturbed by the tongue beating on the 

 edge of the tube, so that the phenomena could not be defined 

 Avith so much precision as they are, when the free reeds are 

 made use of. To discover how the motion of my reed was affected, 

 I therefore adapted a telescope tube ABC, Fig. 17, to a glass 

 portevent DdEeT. Behind the tongue R, but at such a distance 

 as not to disturb its action, I placed a micrometer scale tnn, 

 supported by a wire o, by which I could measure the extent of 

 its excursions towards m, which are very well defined: of course 

 in the other direction they are concealed by the brass reed. 

 I found that the excursions were constant as long as the pitch 

 remained constant: when the flattening or sharpening took place, 

 the excursions were diminished. (See Note B.) The ordinates 

 of the dotted curve above the axis, in Fig. 18. represent the 

 serai-excursions of the reed in this experiment. It was remarked 

 that when the reed was managed so as to produce the double 



• L'Art du Factmr d'Orgues, par D. B. de Celles, pp. 439, 440. (Vide Note E.) 

 Robison, Works IV. 508, and Enc. Brit. Biot, Physique II. 169. 



