MECHANISM OF SPEECH. 561 



the improper diphthongs, as ea, in heat, and in the Latin diphthongs, as <E, in Csesar, one 

 of the vowels is silent. In triphthongs, as eau, in beauty, only one vowel is sounded. 

 I", at the beginning of words, is usually pronounced as a consonant ; but in other situa- 

 tions it is pronounced as e or i. 



A very curious and interesting inquiry relates to the differences, with which we are 

 all familiar, in the quality of the different vowel-sounds when pronounced with equal 

 pitch and intensity. The cause of these differences was studied very closely in the latter 

 part of the last century, but it has lately been rendered very clear by the elaborate and 

 convincing researches of Helmholtz. In this connection, it will be sufficient to indi- 

 cate the results of modern investigations very briefly. When we come to study the 

 physics of sound in connection with the sense of hearing, we shall see that nearly all 

 sounds, even when produced by a single vibrating body, are compound. Helmholtz, by 

 means of his resonators, has succeeded in analyzing the apparently simple sounds into dif- 

 ferent component parts, and he has shown that the quality of such sounds may be modified 

 by reenforcing certain of the overtones, as they are called, such as the third, fifth, or 

 octave. For those who are familiar with the physics of sound, the explanation which we 

 shall give of the mechanism of the production of vowel-sounds will be readily compre- 

 hensible. The reader is referred, however, to our remarks upon overtones in another part 

 of this work, under the head of audition, for a more thorough exposition of this subject. 

 This should be read in connection with what we shall say here of vowel-sounds, when 

 the whole subject will be sufficiently clear. We may pronounce the different vowel- 

 sounds with the same pitch and intensity, but the sound in each is different, on account 

 of variations in the resonant cavities of the accessory vocal organs, especially the mouth. 

 It has been ascertained experimentally that the overtones in each instance are different, 

 as they are reenforced by the vibrations of air in the accessory vocal organs, in some 

 instances the third, in others, the fifth, etc., being increased in intensity. We cannot 

 illustrate this better than by the following quotation from Tyndall, in which modern 

 researches have been applied to the vowel-sounds of our own language : 



" For the production of the sound U (o o in hoop), I must push my lips forward so as 

 to make the cavity of the mouth as deep as possible, at the same time making the orifice 

 of the mouth small. This arrangement corresponds to the deepest resonance of which 

 the mouth is capable. The fundamental tone of the vocal chords is here reenforced, while 

 the higher tones are thrown into the shade. The 7" is rendered a little more perfect 

 when a feeble third tone is added to the fundamental. 



"The vowel is pronounced when the mouth is so far opened that the fundamental 

 tone is accompanied by its strong higher octave. A very feeble accompaniment of the 

 third and fourth is advantageous, but not necessary. 



" The vowel A derives its character from the third tone, to strengthen which by 

 resonance the orifice of the mouth must be wider, and the volume of air within it smaller 

 than in the last instance. The second tone ought to be added in moderate strength, whilst 

 weak fourth and fifth tones may also be included with advantage. 



" To produce E the fundamental tone must be weak, the second tone comparatively 

 strong, the third very feeble, but the fourth, which is characteristic of this vowel, must 

 be intense. A moderate fifth tone may be added. No essential change, however, occurs 

 in the character of the sound when the third and fifth tones are omitted. In order to 

 exalt the higher tones which characterize the vowel-sound E, the resonant cavity of the 

 mouth must be small. 



" In the production of the sound ah ! the higher overtones come principally into 

 play; the second tone may be entirely neglected ; the third rendered feebly ; the higher 

 tones, particularly the fifth and seventh, being added strongly. 



"These examples sufficiently illustrate the subject of vowel-sounds. We may blend 

 in various ways the elementary tints of the solar spectrum, producing innumerable com- 

 posite colors by their admixture. Out of violet and red we produce purple, and out of 

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