the man’s face that we sometimes see, covers the whole, round, bright surface in a good-natured smile thousands of miles wide. That would be a giant! This face is made by the shadows of great mountain ranges, by sunken beds of dried up oceans, and the deep holes of dead volcano craters. It is curious that these hills and holes and shadows should be so placed as to look like a vast face. If you look at the moon through a telescope, or even an opera or field glass, the face disappears, but the things that cause the shines and shadows come out very plainly. Often you can see the mountains on the moon best when it is not full. They stand out, making a jagged or wavy line along the inner edge of the crescent. Astronomers have made maps of the surface of the moon. Knowing the size of the moon, they are able to measure the heights of the mountains by the lengths of the shadows that are cast by them.
WHY BIRDS MOULT
Birds moult, or drop their feathers and grow new ones once a year or, in some kinds twice, for the same reason that you buy new suits of clothes. Feathers wear out. They get dirty and ragged from hard wear in all kinds of weather. Then they do not protect the bird’s skin as well, keep him as healthy, or present as smooth a surface against the wind for flying. All animals moult, some only while growing, some at changing seasons. Fur-bearing animals, horses, cattle, dogs and cats grow thicker coats in winter and shed them in the spring. Snakes, crabs, lobsters and other animals shed their skins because they outgrow them. You shed your skin, but a little at a time, in tiny scales. You can see dead skin roll up when you rub yourself hard after a bath. You shed your hair, too. Old hairs fall out nearly every day, and new baby hairs grow in their places.
WHY PEOPLE BECOME SEASICK
As human beings are land animals their bodies are fitted to live on a stationary base. The sea is always in motion. Anything floating on a big body of water is constantly lifted and let fall and tilted at many angles. This disturbs the nerves of the eyes and the balance or equilibrium of the body, producing dizziness in the head and "sickness" in the stomach. It is probable, too, that the contents of the stomach are more or less shaken by the motion. Many people become just as "seasick" on rocking railway trains as on boats. And
