Resonance, or echo, is produced by the universal law of reflex action which manifests itself in light, sound, etc. How interesting and delightful is the echo! It makes the mountains, like the morning stars, sing together for joy. Listen to a thunder storm among the mountains. There is a sudden explosion, then a silence, as the vibrating waves of mighty amplitude pass over the valley to wake the voice of the mountain beyond, which, standing like a sentinel on guard, speaks in thunder tones to the next, and that repeats the sublime echo until all the mountains join in the chorus, answering back to the heavens. This law of sympathy, undulating from mountain to mountain, so inspired the Greeks that they said the gods spoke to each other from mountain peak to mountain peak. Every pitch in the human voice has its corresponding chamber of resonance, formed by the nares, by the trachea, by the pharynx, or by the mouth, and sometimes by more than one of these. The transient resonant chambers are formed by the adjustment of the lips, and by the relation of the tongue to the upper gum, the hard palate, the soft palate, and the pharynx. With the exception of the pharynx, these and the nasal forms constitute the resonant chambers which produce the different elements of speech in our language. The tone, though smooth when it leaves the vocal cords, may be made harsh by the transient resonant chambers. The nares resound different intervals of the scale in different portions of their length, never resounding two intervals in the same portion. The cultivation of the voice is produced, first, through perfecting the forms of the transient chambers of resonance; second, through establishing perfect freedom and regularity in the action of the vocal cords; third, through developing the rhythmic impulses of the tone. No person ever speaks continuously in a perfect monotone; the pitch is constantly changing with the varying thoughts; as the pitch changes, the resonant chambers change the quality. Nature, unhindered, never reports the same quality on two different degrees of pitch. It is not that the individual, while speaking, intends to change the quality; but nature has so arranged the vocal organs and so determined the laws of acoustics, that unless the voice be interfered with by wrong mental determination, she herself changes the quality as the voice rises or falls.