some external object, to the rose, or the honeysuckle? In answer it may be remarked, if we had always been destitute of the senses of sight and touch, this reference never could have been made, but having been furnished with them by the beneficent Author of our being, we make this reference by experience. When we have seen the rose, when we have been near to it and handled it, we have uniformly been conscious of that state of mind, which we term a sensation of smell. When we have come into the neighbourhood of the honeysuckle, or when it has been gathered and presented to us, we have been reminded of its fragrance. And thus, having learnt by experience, that the presence of the odoriferous body is always attended with the sensations of smell, we form the habit of attributing the sensations to that body as their cause. This mental reference is made with almost as much promptness, as if it were necessarily involved in the sensation itself. Accordingly when we are said to perceive the smell, or to have perceptions of the smell of a body, the three things, mentioned in the definition of perception, are always supposed to exist; (1) The presence of the odoriferous body and the affection of its appropriate organ; (2) The change or sensation in the mind; and (3) The reference of the sensation to the external body as its cause.

§. 38. Of the sense and the perceptions of taste.

A sapid body is applied to the organ of taste. The application of such body immediately causes a change or affection of the sensorial organ; and this is at once followed by a mental affection. Thus we have the sensations and perceptions, to which we give the names, sweet, bitter, sour, acrid, &c.

The affections of the mind are referred by us to something, external to itself, which we call bitter, sweet, &c. as their cause. This reference is made very rapidly, so that we at once say of one apple, it is sweet, and of another, it is sour; but it will always be found to be subsequent, in point of time, to the new mental state. As in the case of smells, which have been already remark

ed upon, the reference is the result of our former experience. We say of one body, it is sweet, and of another, it is acrid, because we have ever observed, that the mental states, indicated by those terms, have always existed in connection with the presence of those bodies.

Whenever, therefore, we say of any bodies, that they are sweet, bitter, acrid, or apply any other epithets, expressive of sapid qualities, we mean to be understood to say, that such bodies are fitted in the constitution of things to cause in the mind the perceptions of sweetness, bitterness, and acridness, or other perceptions, expressed by denominations of taste. Or, in other words, that they are the established antecedents of such mental states, as there is, further than this, no necessary connection between them.

§. 39. Of the sense of hearing and of sounds.

Sounds, which we perceive by means of the sense of hearing, are caused by undulations of elastic air, set in. motion by the sonorous body and striking on the tympanum of the ear.

Sounds differ, first, in the tone; secondly, in the strength of the tone. It is remarked by Dr. Reid, that five hundred variations of tone may be perceived by the ear, also an equal number of variations in the strength of the tone; making, as he informs us, by a combination of the tones and of the degrees of strength, not less than twenty thousand simple sounds, differing either in tone or strength.

In a perfect tone a great many undulations of elastic air are required, which must be of equal duration and extent, and follow each other with perfect regularity. Each undulation is made up of the advance and retreat of innumerable particles of elastic air, whose motions are all uniform in direction, force, and time. Accordingly, there will be varieties in the same tone, arising from the position and manner of striking the sonorous body, from the constitution of the elastic medium, and from the state of the organ of hearing.

Different instruments, such as a flute, a violin, and a

bass-viol may all sound the same tone, and yet be easily distinguishable. A considerable number of human voices may sound the same note, and with equal strength, and yet there will be some difference. The same voice, while it maintains the proper distinctions of sound, may yet be varied many ways by sickness or health, youth or age, and other alterations in our bodily condition, to which we are incident.

§. 40. Manner in which we learn the place of sounds.

Previous to all experience, we should not know, whether a sound came from the right or left, from above or below, from a smaller or greater distance.

Dr. Reid mentions, that once, as he was lying abed, having been put into a fright, he heard his own heart beat. He took it to be some one knocking at the door, and arose, and opened the door oftener than once before he discovered, that the sound was in his own breast. Some traveller has related, that when he first heard the roaring of a lion in a desert wilderness, not seeing the animal, he did not know on what side to apprehend danger, as the sound seemed to him to proceed from the ground, and to enclose a circle, of which he and his companions stood in the centre.

It is by custom or experience, that we learn to distinguish the place of things, and, in some measure also, their nature, by means of their sound. It is thus that we learn, that one noise is in a contiguous room, that another is above our heads, and another in the street. And what seems to be an evidence of this is, that when we are in a strange place, after all our experience, we very frequently find ourselves mistaken in these respects.

If a man born deaf were suddenly made to hear, he would probably consider his first perceptions of sound as originating wholly within himself. But in process of time we learn not only to refer the origin of sounds to a position above or below, to the right or left; but to connect each particular sound with a particular external cause, referring one to a bell as its appropriate external cause, another to a flute, another to a trumpet.

§. 41. Connection of hearing with language.

One of the greatest benefits of the sense of hearing is, that, in consequence of it, we are enabled to hold intercourse with each other by means of spoken language, without which the advancement of the human mind must have inevitably been very limited. 1

It is by means of speech, that we express our feelings to the little company of our neighbours and our own family; and without it this pleasant and cheering intercourse must be almost entirely suspended. Not limited in its beneficial results to families and neighbourhoods, it has been made the medium of the transmission of thought from age to age, from generation to generation. So that in one age has been concentrated the result of all the researches, the combination of the wisdom of all the preceding.

"There is without all doubt," it has been observed, "a chain of the thoughts of human kind, from the origin of the world down to the moment at which we exist, a chain not less universal than that of the generation of every being, that lives. Ages have exerted their influence on ages; nations on nations; truths on errours; errours on truths."

Whether oral language be an invention of man, or a power bestowed upon him by his Creator and coeval with the human race, the ear must in either case have been the primary recipient ;-the faculty of speech so necessary and so beneficial could not have existed without the sense of hearing.

§. 42. Of the sense and the perceptions of touch.

The principal organ of touch is the hand. This part of our frame is composed of various articulations, that by the aid of the muscles are easily moveable, so that it can adapt itself readily to the various changes of form in the objects, to which it is applied.

The senses, which have been already mentioned, are more simple and uniform in their results, than that of the touch. By the ear we have a perception of sounds, or that sensation, which we denominate hearing. By the palate we have a knowledge of tastes, and by the sense of smelling

we become acquainted with the odours of bodies. The knowledge, which is directly acquired by all these senses, is limited to the qualities, which have been mentioned. By the sense of touch, on the contrary, we become acquainted not with one merely, but with a variety of qualities, such as the following, heat and cold, hardness and softness, roughness and smoothness, figure, solidity, motion, and extension.

§. 43. The idea of externality or outness suggested by

the sense of touch:

If man were possessed of the sense of smell alone, it would be found, that the earliest elements of his knowledge consisted exclusively in sensations of odours. According, however, as these sensations were agreeable or disagreable, he would acquire the additional ideas of pleasure and pain. And having experienced pleasure and pain, we may suppose, that this would subsequently give rise to the notions of desire and aversion. But if he had no other sense, all these feelings would seem to him to be internal, to be mere emanations from the soul itself; and he would be incapable of referring them to an external cause.

If he were possessed of the sense of hearing alone, the result would be similar; his existence would then seem to consist of harmony, as in the other case it would be made. up of fragrance; nor indeed by the aid merely of both these senses combined, would he be able to form an idea of externality or outness.

But this idea is a most important one; it is the connecting thought, which introduces us to an acquaintance with a new form of existence, different from that interiour existence, which we variously call by the names, spirit, mind, or soul. This idea first arises in the mind from the sense of touch.

All the senses, not excluding the smell and the taste, which are the least important in a mere intellectual point of view, have their share in bringing the mind into action; they are the primitive sources of thought and of emotion. The mind becomes, in consequence of the senses, full of