as the strings of an Æolian harp are made to sound as they quiver in the wind.

The lowing of the cow, the barking of the dog, and the mewing of a cat, are all produced in a similar way,-the lungs acting as a kind of bellows to the little musical box or organ placed in the throat. Fishes have no such musical box; and even though they had, they could not use it, for the only way in which it can be used is by blowing air through it. The frog cannot make any sound as long as he is under water; he requires to put his head out of the water before he can begin to croak.

3. THE FIVE GATEWAYS OF KNOWLEDGE. THE mind has a kind of telegraphic communication with all parts of the body by means of the nerves, and is constantly receiving messages in this way from the sight, the hearing, the touch, the smell, and the taste. The eyes, the ears, the fingers, the nose, and the mouth, may therefore be termed the five gateways of knowledge; and the nerves are the passages by which knowledge is conveyed to the mind in the brain. Some pėrsons have not åll these inlets for knowledge. For example, some are deaf; in them no knowledge can enter by the ears: others are blind, and no knowledge can therefore enter their minds by the eyes. In the deaf and dumb, the eyes have to do double duty, and many remarkable instances are on record of the amount of knowledge obtained by individuals afflicted by the loss of these senses. One of the most interesting is that of Dr. Kitto, the celebrated author. When a boy, he fell from the roof of a house, and was taken up insen

sible; in which state he continued for a fortnight. He describes his first sensation on recovering consciousness as most agonizing. People seemed to talk, but he could not hear them; they wrote on a slate, but did not speak to him. The poor boy became alarmed, and to complete his sufferings, these words were at last put before him, "You are deaf." The sense of hearing was for ever gone. In after life he himself recorded in one of his books the touching fact, that he never heard the voices of any of his children. Nevertheless, from one thing to another this brave-hearted man struggled on. He afterwards travelled in the East, and made such excellent use of the sense of sight still left to him, that he became the author of some of the most valuable books in the English language on subjects connected with Scripture illustration. A much greater amount of knowledge is obtained by means of the eyes than by the ears: it is, therefore, a greater misfortune to be blind than to be deaf; though it frequently happens that deaf people are very irritable, while blind people are cheerful and contented.

4.-THE NERVES.

THE nerves, which communicate knowledge to the brain, consist of innumerable very small fibres, extending all over the body. These nerves act like the wires of a telegraph, as by them the mind receives and sends out messages to all parts of the body. When we raise our hand, for instance, a message has been sent from the brain to the muscles of the arm, and causes them to act. If we touch anything, the nerves convey a message to the

brain, and tell whether the substance touched is hard or soft, rough or smooth. When we taste anything, the nerves in the mouth inform the mind whether it is sweet or bitter. So, too, when we see anything or hear anything, the nerves of the eye and the ear convey information to the mind.

All the nerves have their beginning in the brain, and they branch out in all directions to every part of the body. No matter how many messages may be coming to the brain, the mind always knows where a message comes from. It never mistakes a message from a finger for one from a toe, nor even a message from one finger for one from another. And so, too, in sending out messages to the muscles, there is no confusion. If we wish to move the hand or the foot, the message always goes to the right muscles. But how all this is done we cannot tell. It is a secret which God has not yet permitted man to find out.

5. THE EYE.

THE eye is an instrument of wonderful beauty, constructed with infinite skill, and consisting of a great many different parts.

It is in the form of a globe or ball; and what we term the white of the eye forms its outer wall, and consists of a strong thick membrane, something like parchment. In front of this is fixed a beautiful little crystal window, through which light first enters the eye. This window is of a round form, bulging out like a watch-glass, and is called the cornea.

Behind this crystal window there floats, in a clear,

transparent liquid, like water, a kind of curtain, called the iris; the chief use of which is to regulate the quantity of light that enters the eye. When the light is very bright, this beautiful curtain is drawn together; and when there is little light it is drawn wide open. The iris or curtain is of different colours in different persons. In some it is blue, and then we say the person has blue eyes. In others it is dark, and then we say the person has black eyes.

The circular hole in the middle of the iris is called the pupil of the eye. It enlarges as the curtain is drawn open, and becomes smaller when the curtain is drawn together. The pupil of the eye is of different shapes in different animals. In man, it is round. In the cat, it is

of this shape.

In the horse, it is shaped in this

way.

The enlarging and lessening, or, as it is termed, the dilating and contracting of the pupil, can readily be seen in the eye of a cat. In the bright sunlight it becomes a

mere narrow slit, like this;

but in the evening it is

wide open, and shaped in this way.

At the back of the iris is a lens, or magnifying-glass, called the crystalline lens, through which light passes

into a dark chamber in the back of the eye. On the walls of this chamber an image or picture of everything before the eye is made, just as images of things are reflected on a looking-glass; but with this difference, that the picture in the dark chamber of the eye is very small, -the picture of a landscape, with all its trees, houses, hills, &c., not covering a space larger than a fourpenny piece!

The nerves that come from the brain to the eye are spread out on the walls of the dark chamber where the picture is made, and serve to convey an impression of it to the mind; but in what way this is done no one can tell.

Above the eye are placed the eyebrows, which, besides being an ornament to the face, prevent the sweat of the forehead from running down into the eye and irritating it. They may be termed the eaves of the roof of the eye's house.

“The eyelids may be compared to a pair of outside shutters for the window of the eye, which we close when we go to sleep, and open when we awake. But these shutters are not useless or merely ornamental through the day. Every moment they are rising and falling, or, as we say, winking. We do this so unceasingly that we forget that we do it at all. But the object of this unconscious winking is a very important one. An outside window gets soiled and dirty, but our eye-windows must never have so much as a speck or a spot on them; and the winking eyelid is the busy apprentice who keeps the living glass clean."

E

1 Professor Wilson.