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than could have been conceived by beings of greater intelligence than man without possession of the organ. The ear, however, is in many respects scarcely inferior either in its importance to us as creatures, or in its capabilities of instruction. Although we cannot derive from its unaided assistance so extensive a knowledge of external nature as from the eye, it offers to man, unimproved by a written language, the only means of receiving a knowledge of the opinions and reflections of his fellows. If it be possible to imagine a state of society in which the individuals are enjoying the blessings of civilization, and possessing all the advantages resulting from an acquaintance with the physical sciences, and the arts attending them, and yet destitute of a written language; it is quite certain that the organ of hearing would be the only medium of conveying the operations of one mind to another. Now even in the present day, and in this country, more advanced in the general education of the people than any other, we may realise the supposition. The majority of the people can read, and have facilities of obtaining books, and yet the number of readers compared with the gross population, is exceedingly small. Knowledge even here then, is chiefly communicated by the agency of the organ of hearing; it is the human voice which teaches best. The ease with which the ear detects sounds and distinguishes between them, is, therefore, of immense importance, altogether independent of its absolute necessity as a means of preserving us from innumerable dangers to which we should otherwise be exposed.

Although the varieties of sound are so numerous and so readily distinguished by the ear, they cannot be described, and we have terms for but few, and even those are generic.

VARIETIES OF SOUND.

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Thus we speak of a snap, a crack, a bounce, a crash, an explosion, a rumbling. But we have no means of distinguishing between the varieties of these, except by using the name of the substance or thing by which it was produced. It is, therefore, customary to say, the crack of a whip, the explosion of a cannon; and in other instances we use a comparative expression, as when we say, like the roll of thunder.

There are, however, two general expressions under which all sounds may be placed-noises and musical sounds. A noise is produced by a series of irregular impulses, and its character is governed by their periods and duration. If they be short, and succeed each other rapidly, we may have an explosion, or crack; if longer and less rapid, a rumble. All the variety of noises may be traced to the length of interval between successive impulses and their duration. Yet the several genera, if we may so call them, are capable of division into species, and habit enables the ear to detect them. There is, for instance, the rumbling sound of distant thunder, and of a carriage; and although in some instances one may be mistaken for the other, in most cases they are readily distinguished.

When the impulses are regular, that is to say, when the same interval of time separates them, and they are all of the same duration, a musical sound is produced.

In estimating the character and peculiarities of musical sounds, there are three things to be considered-the intensity, the quality, and the pitch. The intensity of a sound, is its comparative loudness, and depends upon the violence of the impulses from which it proceeds. From any musical instrument a note may be obtained so loud as to be unpleasant to

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a hearer, or so soft as to be scarcely audible. The only difference between the two sounds is in intensity. When the note obtained from two instruments is the same and of the same intensity, there may still be a difference between the tones. The organ and the flute, for instance, may be made to repeat precisely the same sounds and with the same intensity, yet an ear but little practised would instantly detect a dissimilarity of character-this is called quality. Sounds produced from the same instrument may be of different qualities. We can scarcely estimate how much a musical performance depends on the quality of the sounds. Two persons may play the same air, and with equal accuracy; yet in one case we may be struck with the roughness of the tones, and in the other with their full and mellow harmony. In musical performances, the quality of sounds will depend partly upon the capabilities of the player, and partly on the instruments. Every one knows that some instruments are very preferable to others, and this is only because the sounds obtained from them are of a richer quality.

The pitch is altogether independent of both intensity and quality, which may be different in the same sound. When we strike two or three adjoining strings on the harp or the violin, we detect a difference in the sounds that cannot be attributed to either the greater loudness or sweetness of one than another-the sounds are in fact essentially different, they are not of the same pitch. When any two or more notes are of the same pitch, they are said to be in unison.

We have already explained that sound is produced by vibrations excited in some sonorous substances. By successive impulses on a conducting medium, the effect is transmitted to the

PRODUCTION OF MUSICAL NOTES.

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ear, and there excites the organ of sensation. A succession of impulses less frequent than sixteen in a second, is incapable of affecting the human ear, Sounds of different pitch, or in other words, different notes, are attributable to the rapidity of the vibrations. A certain number of vibrations in a second will always produce the same note, whatever may be the instrument used in obtaining the vibrations.

For the production of a certain musical note, the sounding body must be in a particular state-that state, in fact, suited to the production of a fixed number of vibrations in equal times. That a string should give out, when touched, a note of any pitch, it must have a fixed length, tension, and density; and if either of these be changed, the note is also instantly altered. All these elements are important, because the number of vibrations is regulated by them. Tuning an instrument, therefore, is nothing more than bringing the vibrating or sounding body into such a state, that a certain number of oscillations may be performed in a given time.

The human ear is not sensibly affected by all sounds. There are some notes so low that they are indistinct murmurs, and some so high that they cannot be heard at all; in the one case the vibrations are slow, and in the other rapid, but in both, the organ of hearing is alike incapable of transmitting the impression.

Dr. Wollaston made some curious observations which he communicated to the Royal Society in the year 1820, on the inaudibility of certain ears to particular sounds. This very accurate observer discovered, that persons who have, in the ordinary acceptation of the phrase, a perfect hearing, may at

the same time be completely insensible to those sounds which are at the extremities of the scale of musical notes. The loudness of the sound has, it is said, nothing to do with this effect; it depends entirely upon the pitch. Deaf persons, as is well known, hear some sounds better than others, generally those which are sharp and clear. They hear women and children more distinctly than men. It may be remarked, says the Doctor, that the generality of persons accustomed to speak to those who are deaf, seem practically aware of this difference; and, even without reflecting on the motives which guide them, acquire a habit of speaking to deaf persons in a shriller tone of voice, as a method by which they succeed in making them hear more effectually than by merely speaking louder.

It appears from the memoir, an abstract of which we are giving, that its author was first led to the subject by a desire to ascertain the origin of deafness in a friend. To do this, he sought to decrease the sensibility of his own ear, and found "that when the mouth and nose are shut, the tympanum may be so exhausted by a forcible attempt to take breath by expansion of the chest, that the pressure of the external air is strongly felt upon the membrana tympani; and that in this state of tension from external pressure, the ear becomes insensible to grave tones, without losing in any degree the perception of sharp sounds." By frequent attempts, he was able to keep the ear in a state of exhaustion without stopping the breath; and could always restore an equality of pressure, and consequently remove the partial deafness, by the act of swallowing, which re-opens the tube. In this way he succeeded in making his

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