394 CONSONANTS. 



it will be recognised even if the series of vowels are successively 

 pronounced in a low voice, whereby it may be proved that the sound 

 of the cavity of the mouth remains the same, whatever the pitch of 

 the larynx- sound proper. 



The vowel sounds of the cavity of the mouth may be 

 also rendered audible by blowing a broad current of air 

 across the lips or upon the sharp edges of the teeth, that 

 is, in the same manner as the notes of a column of air 

 in a tube. For this experiment, however, much practice 

 is required, and the bellows used for it must be capable 

 of producing a lasting and invariable current of air. 



Certain consonants also may be produced without 

 interrupting the current of expired air, by modification 

 of the form of the throat and mouth. Thus the aspi- 

 rate H is the result of a* little extra expiratory force 

 a sort of incipient cough. S and Z, Sh and /", 

 Th, L, R, F, V, may likewise all be produced by 

 continuous currents of air forced through the mouth, 

 the shape of the cavity of which is peculiarly modi- 

 fied by the tongue and lips. The sounds M and N 

 can only be formed by blocking the current of air 

 which passes through the mouth, while free passage 

 is left through the nose. For M, the mouth is shut by 

 the lips; for JV, by the application of the tongue to the 

 palate. The other consonantal sounds of the English 

 language are produced by shutting the passage through 

 both nose and mouth; and, as it were, forcing the ex- 

 piratory vocal current through the obstacle furnished 

 by the latter, the character of which obstacle gives 

 each consonant its peculiarity. Thus, in producing the 

 consonants B and P, the mouth is shut by the lips, 

 which are then forced open in this explosive manner. 



