NAT. HIST. DIV.); by dilating or contracting the mouth ; by contract ing the communication between the pharynx and mouth so as to make them distinct chambers, or by dilating the opening so as to throw them ioto one, which is chiefly effected by movements of the soft palate ; by altering the form of the mouth's cavity, which is produced by varying the position of the tongue. It will be found that each of these modifications of the vocal tube confers a peculiarity of quality to the voice. All these, however, are vocal or laryngeal sounds.
Sounds can be produced in the vocal tube apart from the larynx. These are not vocal sounds. Some of them, however, may be of a definite and uniform pitch, while others are mere noises, as rustling, whisper ing, gurgling, whistling, snoring, and many others.
Now, as every audibility comes under the classes of noise, sound, or musical sound, and as each variety under these classes is producible by the vocal apparatus of man,it is an obvious conclusion that an ordinary vocal apparatus is all that is required to vocalise the mimetic con ceptions of the ventriloquist. A larynx capable of producing a larger compass of voice than another has a greater range of pitch within its power of imitation.
A person having an ear acutely perceptive to the nice distinctions of sounds may, by a little practice, imitate many sounds with accuracy. Those persona, however, who are highly endowed with the mental requisites, which consist of an intense desire to mimic, coupled with the ability to originate mimetic ideas, are able to imitate sounds at first hearing, and without previous practice. Passing from the imitation of sounds, as that of knife.grinding, sawing and planing wood, the voices of animals and men, we proceed to treat of those illusions where the voice so perfectly counterfeits the reality intended, that it appears not to issue from tho mimic, but from an appropriate source, in whatever direction and at whatever distance that source may be. The essence of ventriloquy consists in creating illusions as to the distance and direction whence a sound has travelled ; which are thus explained : I. Distance. We do not hear the distance which a sound has
travelled from its source, but we judge the distance from our former experience, by comparing the loudness which we hear with the known distance and known loudness of similar sounds heard on former occa sions. Common experience will confirm, that we oftener err in estimating the distance of uncommon than of familiar sounds. In apology for such an error the ordinary language is, " It seemed too loud to come so far," or " It seemed too near to be so faint a sound," as the case may be. Both of which are apologies for an erroneous judgment, and not for hearing.
Near sounds are louder than distant ones. Now, by preserving the same pitch, quality, and duration, but ..with an accurately graduated reduction of loudness, a series forming a perspective (if the term be allowable) of sounds may be created, which, falling in succession on the ear, will suggest to the mind a constantly increasing distance of the sound's source.
Loudness is a property of sound which has not had justice done to its importance in the schools of music and elocution. Its nomenclature is vague and meagre, and it can scarcely be said to have a notation. The author of this article has observed that one of the high excellences which singers of genius have snatched beyond the rules of art has been a skilful management of the degrees of vocal loudness, and a nice adaptation of them to aid the melody in expressing the intended feeling. The varieties of loudness remain still unmeasured, and the abrupt transitions in loudness made by musical performers suggest that these distinctions are ill perceived.
The estimate, then, which is formed of the distance which a sound has travelled before reaching the ear is a judgment of the mind formed by comparing a present perception (by hearing) with the remembrance of a former loudness in connection with its known distance.