quist consists in nothing but the power which a nice and accurate ear gives him, of distinguishing the difference between sounds when near, or far off, and of imitating them.

Touch.

The sense of touch is not confined to one particular organ, but is extended over the whole system, both externally and internally. It is in the hands, however, especially at the ends of the fingers, where this sense is most acute and most employed. We acquire many more ideas by the aid of this sense, than by either hearing, smell, or taste. By these last we become acquainted with only one particular quality in a body, either of taste, smell, or sound; but by means of the touch, we learn such qualities as heat and cold, roughness and smoothness, hardness and softness, figure, solidity, and extension. It is supposed, that it is by this sense, that we gain the idea of something external, or without ourselves. The sensation of smell would seem to be within, as an act or emotion of the soul itself. Thus also with hearing, which being produced within the ear, by the undulating air, would seem to originate within. Thus also with sensations within the eye. But when the limbs begin to move and to come in contact with outward objects, and also in contact with various parts of the body, the mind gains an idea of the existence of some outward object. This is probably the first sense, by which any idea of existence is wakened in the mind. As one sense after another is called into existence, the mind continually gains new ideas, and then begins its operations of comparing, abstracting, reasoning, and willing.

It is by the sense of touch, that we gain our ideas of resistance and extension. In the class of ideas included under the head of ideas of resistance, may be placed our ideas of solidity, liquidity, hardnesss, softness, viscidity, roughness and smoothness; these all being different names for different modes of resistance to the muscles of the hands, arms, or

fingers, when applied to the bodies which have these qualities. These ideas are not gained by simple contact; their existence depends upon the contraction or expansion of the muscles which are the organs of motion and resistance, in the human body. We may suppose the infant mind to gain these ideas by a process somewhat similar to this: He first moves his arms by instinct, without any knowledge of the effects to follow. By this movement, he gains certain ideas of the simple contractions and extension of his muscles, and learns also, that by his own will, he can exercise his muscles in this manner. At length he attempts to move his arm in a manner to which he has become familiar, and some object intervenes, and this motion is prevented, while all his wonted muscular efforts are vain. Thus then arises in his mind a new idea of resistance, in addition to the sensation of touch and of motion, which had before been experienced. The ideas of different· degrees of this resistance are gained by repeated experience, and when age furnishes ability to understand language, the names of hardness, softness, roughness, and the like, are given to these ideas. In the use of his muscles also, the infant must first acquire its ideas of extension and figure. For it must be where resistance to muscular effort ceases, that he must feel that the cause ceases to exist. The little being extends his hand-an object intervenes which interrupts his muscular motions-he grasps this object, and wherever this feeling of resistance exists, there he feels that the cause of it exists, and that after he has passed certain limits it does not exist. Figure is defined as the limits of extension, and of course it can be seen that ideas of figure can only be gained by finding the limits of extension in this way. It has formerly been supposed that ideas of extension and figure were gained by the eye, but later experiments and discussions show, that the sense of feeling, including muscular motion, is the medium by which these ideas are first gained, and that afterwards the eye, by the principle of association acquires the power of distinguishing figure and distance.

Vision.

The organ of vision is the eye, which is one of the most curious and wonderful parts of the human frame, and displays in astonishing variety the wisdom and skill of its Designer.

The eye consists of a round ball, formed externally, of various coverings, and within, of humours of different degrees of consistency. The front part of the eye, which is exposed to view, has a small opening in it, which admits the rays of light within this ball, and it is by the operation of light on the nerves which are spread in fine net-work over the interior that sight is produced.

In examining the mechanism of the eye a great variety of contrivances appear; all aiding in accomplishing the object of vision. In the first place, we may observe its modes of protection and defence. The lid is a soft moist wiper, which with a motion quick as lightning, protects the eye from outward violence, cleanses it from dust, veils it from overpowering radiance, and in hours of repose entirely excludes the light. On its edge is the fringing lash, which intercepts light floating matter that might otherwise intrude, while above is spread the eyebrow, which like a thatch, obstructs the drops that heat or toil accumulate on the brow.

We next observe the organs of motion with which the eye is furnished, and which with complicated strings and pullies, can turn it every way at the will of the intelligent agent. The pupil or opening of the eye, also, is so constructed, with its minute and multiplied circular and crossing muscles, that it can contract or expand in size, just in proportion as the light varies in intensity.

The ball of the eye is filled with three substances of different degrees of density. One is a watery humour near the front of the eye; back of this and suspended by two muscles is the solid lens of the eye or the chrystalline humour, and the remainder of the eye in which this lens is imbedded, consists of

the vitreous humour, which is of the consistence of jelly. These all have different degrees of transparency, and are so nicely adjusted, that the rays of light which start from every point in all bodies, in diverging lines, are by these humours made to converge and meet in points on the retina, or the nerves of the eye, forming there a small picture exactly of the same proportions, though not the same size, as the scene which is spread before the eye.

If an eye is taken and examined by the aid of surgical instruments, when the outer covering of the back part of the eye is removed, the objects which are in front of the eye, may be discerned, delicately portrayed in all their perfect colours and proportions, on the retina which lines the interior of the eye. It is this impression of light on the optic nerve of the eye which gives our ideas of light and colours.

The eye is also formed in such a way that it can alter its shape and become somewhat oblong, while at the same time the lens of the eye is projected forward or drawn back. The object of this contrivance is to obtain an equally perfect picture of distant and of near objects, which is thus secured.

Our ideas of shape and size at first are not gained by the eye, but by the sense of touch. After considerable experience, we learn to determine shape and size by the Exeye. periments made upon persons born blind and restored to sight furnish many curious facts to support this assertion.

When the eye first admits the light, all objects appear to touch the eye, and are all a confused mass of different colours. But by continual observation and by the aid of the sense of touch, objects gradually are separated from each other, and are then regarded as separate, and distinct existences.

The eye is so formed, that the picture of any object on the retina varies in size according to its distance.-Two objects of equal size, will make a very different sized picture on the back of the eye, according to the distance, at which they are held. The ideas of size, at first are regulated by the relative

size of this picture in the eye, until by experience it is found that this is an incorrect mode, and that it is necessary to judge of the distance of a body before we can determine its size. This accounts for the fact, that objects appear to us so different in size according as we conceive of their distance, and that we are often deceived in the size of bodies, because we have no mode of determining their distance. But it appears also that our ideas of distance are gained not by the eye alone, but by the eye and the sense of feeling united. A child by the sense of feeling, learns the size of his cup, or his play-things. He sees them removed and that their apparent size diminishes. They are returned to him, and he finds them unaltered in size. When attempting to recover them, he finds that when they look very small he is obliged to pass over a much greater distance, to gain them than when they appear large, and that the distance is always in exact proportion to their apparent size. In this way by oft repeated experiments the infant reasoner learns to judge both of the size and distance of objects. From this it appears, that in determining the size of an object, we previously form some judgment of its distance, and likewise that in finding of the distance, we first determine the size.

'The shape of objects is learned altogether by the sense of feeling.

It has before been stated that at the first exercise of vision every thing is a confused mass of different colours and all appearing to touch the eye. By the aid of the hands, the separate existence of different bodies around is detected and the feeling of touch which once was the sole mode of determining shape is now associated with a certain form or picture on the eye, so that in process of time the eye becomes the principal judge of shape.

But in determining the shape of a thing, an act of judgment is necessary. This may be illustrated by the example of a hoop, which in one position, will make a picture in the eye