402 MANOMETRIC FLAMES. 



ceptible overtones. This appearance is obtained "by 

 humming a note into the tube, or by singing or speaking 

 into it the vowel-sound 00 (as in cool). If the gamut is 

 sung in this vowel-sound, beginning with the lowest 

 note of the scale, and turning the box at the same 

 time as uniformly as possible, the images will be seen 

 to approach more and more closely to one another, 

 Although the note / is sounded by the cavity of the 

 mouth when 00 is sung^ the effect of it is too weak to 

 exert any perceptible influence upon the flame. 



It is different when (as in. oh) is sung, for in this case 

 the note bb' is sounded by the cavity of the mouth while 

 is sounded by the larynx, and the former note influences 

 the flame in some measure; hence the appearance of 

 the images is different. If the pitch in which the 

 vowel is sung is varied, the images not only vary their 

 relative distance, but their whole appearance is changed. 

 The reason of this is that only one note, viz., that pro- 

 duced by the larynx, varies in pitch, while that produced 

 by the cavity of the mouth remains unaltered through- 

 out ; in other words, the images, or rather tongues of 

 flame, which correspond to the larynx-sound, alter the 

 relative distances between their points when the pitch 

 changes, while the points of the images which are pro- 

 duced by the cavity of the mouth sounding fo' maintain 

 throughout the same distances from one another. The 

 image becomes most instructive if is sung on the 

 note V? 



*J fe- 

 ll! that case the larynx-sound is iust one octave 



