They are little folds of skin fringed with hairs, which we can shut up so as to cover the eyeball and keep out the light when we want to sleep or when we are in danger of getting dust or smoke into the eye.

The hairs placed along the edge of the lids help to keep the dust out when the eyes are open.
~17.

The Eyebrows.~--The row of hairs placed above the eye is called the eyebrow.

Like the eyelids, the eyebrows catch some substances which might fall into the eye, and they also serve to turn off the perspiration and keep it out of the eyes.
~18.

The Tear Gland.~--Do you know where the tears come from?
There is a little gland snugly placed away in the socket of the eye just above the eyeball, which makes tears in the same way that the salivary glands make saliva.