THOUGHT A VAGUE TERM.

113

-a law

rous reflex acts subservient to the well-being of the body, varied as these constantly are in man and animals, under successive changes of circumstances. Such acts, and instinctive acts, fall under the same great law of the nervous matterunquestionably originally impressed upon it by the fiat of the Creator. "As, then," says Dr. Bushnan (Philosophy of Reason and Instinct), "certain organic acts are the direct effect of sensation, so it will be found that instinctive acts, properly so called, can be traced to the same cause, and are, like them, dependent either on external or internal stimuli." The great sources of instinctive acts in the lower animals, are the senses of smell and taste; by which, particularly the former, they are led to select food which is salutary, with a certainty which far exceeds the boasted knowledge of man. There is scarcely a plant which is not refused by some, while it is eagerly sought after by others; and as many of these plants are highly poisonous to man, we must here draw the striking conclusion, that when the instinct of an animal leads it to eat of a plant poisonous to others, the law which so directs it, through the unconscious nervous centre, must embrace the fact that the poisonous chemical principle of that plant is destroyed by the peculiar digestive power of that animal.

Finally, among the sources of sensation on which instinctive acts are dependent, are various qualities of the atmosphere at different seasons, the periodical returns of appetites, and particularly of the sexual desire, the sense of ungratified want, the consciousness of muscular action, and, in higher animals, the presence of all kinds of emotion.

Thought. When spoken of in connection with the functions of relation, Thought has an extensive signification. It is then contrasted merely with sensation; so that sensation and thought are often employed to include all mental phenomena. Such a use of the term thought, is, however, merely for the sake of temporary convenience; since emotions, passions, desires, and appetites-all of which are states of consciousness, distinct from sensations, can with no propriety be deliberately regarded as thoughts. If, however, from the whole succession of a man's states of consciousness we subtract his sensations, his emotions, his passions, his desires, and his appetites, then those states of consciousness which remain, will be such as are most appropriately termed thoughts. Thus, then, an act of memory is a thought; an act of conception is a thought; an act of abstraction is a thought; an act of imagination is a thought; an act of judgment is a thought;—and to think is specially to determine, with some definite purpose, successions of these several kinds of acts.

When a person thinks over a subject, he puts it in all possible lights, endeavouring to find out each new relation in which it stands ;—that is, making use of what he has observed as to the modes in which one thing suggests another, he makes those things which rise spontaneously in his mind, the means of bringing up other things which were less obviously connected with his first thoughts.

Thinking, then, is a succession of acts, only in part voluntary. A man cannot call up any thought at pleasure unless within very narrow limits. But when he has once got possession of a thought, by dwelling on it, and considering its several connections, he may be secure that it shall arise whenever certain other thoughts shall have first occurred to his mind. When a man thinks correctly on any subject, it is very mucb. the same as to say he exercises reason on that subject. For, to think correctly, he must exert a certain control over his thoughts, rejecting those which are vain, frivolous, and not pertinent to the subject, and detaining those in the contrary predicament. Still the mere expression to think has no constant reference to the exercise of reason since one mav be said to think in the larger sense when the thoughts suggested to the mind by

ORGANIC NATURE.-No. IV.

114

EDUCATION CONTROLS THOUGHT.

some subject rise freely, whether they be to the purpose or not. Thus it is quite correct to say, that a man thinks incorrectly; and in so thinking he may have exercised actually as much voluntary control over his thoughts, as in any profound and just meditation. But to say that a man exercised his reason incorrectly, involves a contradiction. Thus, to think and to exercise the reason, are not one and the same thing. The reason, indeed, cannot be exercised without thinking; but much thought may pass through the mind with very little exercise of reason.

What is commonly called a train of thought presents this term in its widest signification. We say currently a train of thought is dependent on the association of ideas. But, when a train of thought is reviewed-for example, such a train as constitutes a reverie-it is found to consist not merely of the states of consciousness commonly called thoughts, or of those expressed by the term ideas, but of states of consciousness of every known kind-sensations, memories, abstractions, conceptions, imaginations, judgments, pity, remorse, anger, jealousy, ambition, desire. And each of the states entering into such a train is linked or associated with the states adjacent to it in the succession; so that what is usually called the association of ideas, is really the order in which the succession of every kind of consciousness happens at any one time to be determined.

Every man has his trains of mental phenomena, to a certain extent, under his own power, and this is the foundation of all self-education, or rather the foundation of all moral and intellectual education. It is quite possible that a child may be so reared as to be incapable of conforming the conduct of after life to the standard of morals required by the laws of his country. This person is exactly in the condition of him who labours under moral insanity. Had the dispositions, in childhood, of such a person been restrained by judicious management, then the passions, desires, and appetites would have been reduced within those bounds which reason requires. When the natural disposition is such, that under the best direction a child grows up, totally incapable of subjecting his moral nature to the control of reason, then that person is morally insane from birth.

The intellectual nature is perhaps less under the control of management than the moral nature. Nevertheless, education is capable of greatly extending the range of thought, and, within somewhat narrow limits, of giving to it greater justness and exactness than naturally belongs to the individual.

The benefits of training, whether by the education imparted from without, or by the efforts of the individual himself towards self-improvement, are manifestly dependent on the changes accomplished on the natural succession of the states of consciousness, or, in common language, on the natural succession of thoughts. And it is manifest that the more any one has indulged in incorrect thinking, or in licentious wishes, before the corrective of training is applied, the more difficult it must be to bring back the current of his intellectual and moral nature to that which reason directs. Correct thinking, intellectually and morally, is the only foundation of just judgment and blameless conduct :—

"For since the course

Of things external acts in different ways

On human apprehension, as the hand

Of nature tempers to a different frame

Peculiar minds; so, haply, where the powers

Of Fancy neither lessen nor enlarge

The images of things, but paint in all

Their genuine hues the features which they wore

In nature-there opinion will be true,

And action right."—AKENSIDE.

VOICE AND THE SOURCES OF SOUND.

115

The next and last function we have to consider is that of speech, or the sounds which are produced in the larynx or vocal apparatus at the moment when the air traverses this organ, either to enter or to pass out of the trachea or windpipe; and we shall distinguish speech in man from the cries, song, and buzzing of inferior animals.

Voice. Without the possession of voice how different would have been the history of man's progress on the earth! We can hardly conceive any other effectual kind of speech except that to which voice is subservient. Without articulate sounds man could hardly have risen to the rank of an intelligent thinking agent. By means of expression and gesture he might have communicated to his fellow-men no small share of his present desires, his present feelings, and even his present rude ideas; but under such circumstances how little of the past-how little of the future-would have entered into his mental existence !

Speech, then, may be justly regarded as one of the principal foundations of man's greatness upon the earth; and thus voice, speech, the cries of animals, the song of birds, and the buzzing of insects, present, in a physiological point of view, a succession of themes of the most engrossing interest.

In physiology voice is distinguished from speech, though without voice there is no perfect speech. This point deserves a word of explanation. When a person can speak only in a whisper, he is said to have lost his voice; that is, he has lost the power of utterance with that loud, thrilling, vibratory sound which constitutes perfect voice. But if whispering were man's only natural mode of speech, then we should not be entitled to say that man had no voice, but only that his voice was a soft, hissing, nonvibratory sound.

Voice, then, whether it be soft and hissing, or loud and vibratory, is formed in the larynx. Speech is the voice modulated in its passage through the mouth and nose by the agency of particular organs, such as the tongue, the palate, the teeth, the lips. It is conventionally only, and for the sake of convenience, that physiologists speak of a whisper as being speech without voice, that is, without vibratory voice; and of those who speak only in a whisper, as having lost their voice, in contradistinction to those unfortunates who suffer under a loss of speech, which properly constitutes dumbness.

Dumbness originates exclusively from original defect of hearing-thus indicating the intimate connexion between the gift of articulation and the perfection of that sense. Again, the capability of the dumb (deaf-mutes, as with something akin to an affectation of precision they are now often called) to acquire the use of speech, rude as it commonly is, shows how largely the organs concerned are placed under the control of the will.

The Sources of Sound. The organs of the voice and of speech are analogous to instruments of music, so that some preliminary observations on the sources of sound become requisite.

In every case sound is derived from the vibration of a body. It is, however, erroneous to describe sound as merely a vibration of the air. Most sounds, it is true, reach the ear through the vibration of the air, whether they have had their source in the air, or in some body with which it is in contact. It is usually said, that a bell has little or no sound in a vacuum. This is in so far true; for unless a communication is made between the ear and the bell independently of the air, little or no.sound would be heard. But if a cord or some similar body be stretched between the bell and the ear, and particularly if the external cavity of the ear be previously stopped with some substance, such as chewed paper, which the cord is made to touch, the sound of the bell will be distinctly heard. In such a case no part of the communication of the vibrations

116

SOUND NOT MERELY A VIBRATION.

of the bell is made through the air-the membrane of the tympanum or drum of the ear receives the vibrations and transmits them through the chain of little bones to the labyrinth or most interior part of the ear, where, by means of undulations excited in the fluid in contact with the subdivisions of the auditory nerve, the requisite impression is made.

Many other instances may be cited of sounds produced by the vibrations of solid bodies being conveyed to the ear without the intervention of the atmosphere. For example; when a tuning-fork is made to vibrate and placed between the teeth, the sound is conveyed from the teeth, through the bones of the face and the head, to the auditory nerve. Also when a solid-vibrating body is suspended by a cord which is brought into contact with the teeth, the sound is heard independently of the atmosphere. Again, when a sounding body is suspended between two cords reaching to the ears, the influence of the air is excluded. When a cord is extended from a sounding body to some part of the head, particularly to such parts as are sparingly covered with soft substance, the sound is heard without the assistance of the atmosphere. When a watch touches the teeth, particularly of the upper jaw, its ticking is distinctly heard on the same principle. When the watch is applied to the tongue, the sound is much fainter. We find it stated that the vibrations of a metallic spoon were heard at the distance of three hundred yards by means of a cord extended to the ear. We are told that the sound of distant cavalry is heard much better when the ear is applied to the ground than when the listener stands erect. In cases of this kind, where the sound is conveyed along the surface of the ground, it is to be understood that the sounds are produced in the ground itself, or in solid bodies communicating directly with the ground.

Vibrations are also communicated from water to the ear without the assistance of the atmosphere. For example; in bathing, when the head is plunged under water, distant sounds produced in the water are heard distinctly. When, however, sounds proceed from water into air, the effect produced on the air is faint.

The sounds which reach the ear through the atmosphere may originate in vibrations of the air itself, or may have been communicated to it by the vibrations of liquid or of solid bodies. And this, doubtless, is the common case. Nevertheless, it is plain, from what has been above stated, that to describe sound as a vibration of the air is to view it in too limited a sense.

To produce sound the vibrations must be of a certain strength; for it is plain that a body often continues to vibrate after it has ceased to emit sound. Sounds pass through air with less rapidity than through water, and through water with less rapidity than through solid bodies. For example; the sound of a hammer struck at the top of a high house is heard double by a person standing on the ground below; that is to say, the first sound which reaches his ear is conveyed through the solid materials of the house, while the second sound is transmitted through the air to his ear. It is observed, also, that on the approach of a heavy waggon in the street the furniture of a house begins to shake before the noise of the waggon is heard.

The velocity of sound in air is estimated at 1130 feet per second-in water at 4708 feet in the same unit of time. The velocity of sound conveyed through solid bodies appears to vary much according to the texture of the substance. From some experiments, it appears to pass through deals of fir-wood at the rate of 17,400 feet per second, which is upwards of three miles.

When a sound is produced in an open space, it is more short and sharp than when in a room; because, when a sound occurs in a room, the vibrations of the air which

VOICE SHARPER IN THE OPEN AIR.

117

strike against the walls and furniture excite new vibrations in these bodies, which, being again communicated to the air, affect the ear in close succession with the original vibrations, and so prolong the sound. This effect is termed the reverberation of sound. When there are no bodies near at hand to reverberate the sound, but a body or bodies at a distance capable of that effect, an echo is produced. Thus an echo may be described as a reverberated sound, which does not reach the ear until the primary sound has ceased. An echo may take place from a wall, a rock, a grove of trees, and, as it is said, even from a cloud; and also, as it would seem, from condensed air. If an echo can take place from a cloud, it is an example of an echo produced by the vibrations of water in its liquid state. The body from which a distinct echo takes place must be at a considerable distance, and there must be no interposed bodies capable of keeping up the succession of vibrations. In every large and lofty empty room there is a species of imperfect echo, owing to the want of furniture to keep up the succession of reverberations between the termination of the primary sound and the reverberations from the walls and roof. The echo of a monosyllable requires a less distance than the echo of a dissyllable; it is estimated that the distance required for a monosyllable is 80 feet, that for a dissyllable 170 feet.

A musical sound is to be distinguished from a noise. A noise consists either of a single powerful concussion or report, or else of an irregular repetition of such sounds. A musical sound consists of a number of synchronous vibrations; that is, of vibrations occupying the same minute period of time. The vibrations in a musical sound are not all of the same extent; but whether great or small, each occupies the same period of timein short, they are like the vibrations of a pendulum, which, whether great or small, are performed in the same space of time, when the pendulum is of a definite length. Sonorous undulations may be described as of two sorts-namely, curved and molecular. We have an example of curved undulations when a string, fd g, fastened at both ends, a b, so as to be tight, is drawn to one side at its middle point. By this retraction the string, which was before straight, is now bent into a curve, af d g b. When let go it not only

recovers its former position, but passes to the other side, assuming the same curved form, a f" d" g" b, into which it was at first drawn; and thus it continues to vibrate from side to side, alternately forming a curve, with a gradual diminution of extent on each side of its original position. So long as these vibrations are of considerable strength, a sound is emitted; but, as before observed, the sound ceases before such a string returns entirely to rest. To produce an impression on the ear, but a moderate velocity in the vibrations is necessary. It appears that a sound may remain audible with a velocity of no more than Toth part of an inch in a second: perhaps it may be heard even with a much smaller velocity than this. Nevertheless, in such a case it is probable that the initial velocity must be considerably greater than that here described.

What is termed molecular undulation is exemplified in the alternate condensation and rarefaction of air.

When we blow into a tube open at both ends, the air contained first becomes