four hours to go once round on its axis. This is why we have about twelve hours of sunshine and twelve hours of night.
For Recitation.—How does the earth move? How long does it take to turn round? When do we have daylight? When do we have night? Does the sun really come up every morning and go down every evening? When the sun rises, what is happening? And when the sun sets, what is happening?
LESSON XI.
THE SEASONS.
Preparatory Oral Work.—Use again oranges or balls, hat-pins, and candles. Move the globes around, keeping the north pole always pointing in the same direction, and name the seasons. Then turn the ball on its axis as you carry it around the candle, so as to teach the class how both motions are going on at the same time. Let each pupil make the experiment. Ask who can do this at home to-night.
On the first Monday in each month, at twelve o'clock, measure the length of shadow of a perpendicular pole and record it. Measure the distance that the sun shines into the south window and record it. The shadows will be longest in December and shortest in June.
Notice that the axis of the orange always slants the same way. For this reason at 2 the light shines on the top of the orange; at 4 on the bottom; at 1 and 3 equally on both top and bottom
1. The Earth Revolves.-Besides turning round on its axis, the earth moves in another way. Let us try to understand this movement. Suppose we draw a large chalk ring on the floor, or on the top of a large table, and then put the lighted lamp in the middle of the ring.
Now let us walk round the ring, holding the orange with the knitting-needle through it, so that the light of the lamp shines on it.
What we are now doing with the orange shows what happens to the earth. Nobody marks a ring for the earth with chalk, but still it goes in a ring, round and round the sun, as the orange does round the lamp. Nobody carries it, as we do our orange. It goes of itself, but it never gets tired and never stops.
It is only a few feet round our chalk ring. It is millions of miles round the earth's ring.
It takes us only a minute or two to carry our orange round the lamp. It takes the earth a whole year, all the time from one of our birthdays to another, to revolve around the sun.
1. The Seasons.—Now as the earth moves in its ring round the sun, sometimes our country receives more sunshine and heat, and sometimes less.
At one time the swallows come. The birds build their nests. The people are planting and sowing. It is now not very hot and not very cold. It is spring. The orange at 1 in the picture shows where the earth is in its path at this time.
In a very short time there comes a change. The days grow longer, the weather gets warmer. The trees are full of fruit, the melons are ripe. It is summer. The orange at 2 in the picture shows where the earth is in its path at this time.
Months pass. The leaves turn and begin to fall. The yellow corn is gathered in. Thanksgiving Day comes. It is autumn or fall. The orange at 3 in the picture shows where the earth is in its path at this time.
Again there is a change. The days grow shorter, the weather gets colder. Snow covers the hills; ice covers the ponds. Christmas and Santa Claus come. It is winter. The orange at 4 in the picture shows where the earth is in its path at this time.
These four parts of the year—spring, summer, autumn, and winter—are called the four seasons.
In some countries there are only two seasons, called the wet and the dry. In others there is one long winter with scarcely any summer.
For Recitation.—Besides turning on its axis, how else does the earth move? How long dues it take the earth to go round the sun? What changes in the weather take plaec as we go round the sun? What, then, may we say is caused by the earth's revolving round the sun? How many seasons have we? Have all parts of the earth four seasons?
