XXI. PUSHES AND PULLS LOOK! Here is somebody tugging with all his might! He thinks he can start that rock. He knows that if he can it will go of itself the rest of the way down the hill. If he had loosened the earth on the lower side, it would have been easy, for the rock would then have gone of its own accord. At last he put all his strength into a quick pull on the other side. He felt the stone move; then he sprang aside to keep The big stone rolled and It was in danger of going himself from going with it. tumbled. What made it? past the place where Johnnie wished to have it stop. "You were hard to get waked up,” he said, “but now you are too strong for me." The boy had used all his little stock of strength, and he lay down to rest and get it back again before he did the next thing he had in mind. What about the rock, — did it get tired? PUSHES AND PULLS 47 Push! Pull! Shove! Tug! Hold! Lift! These are words of command, they tell that strength or force with a will is called for. What an odd thing strength is! Johnnie lying there on his back does not show an ounce of it. The stone at the foot of the hill does not seem to have it. earth was young it worked with tremendous power. It tore up mountains, it lifted valleys, it crushed forests. It does such things even now in our time. When the earth was young, people called these powers gods. Nowadays we know they are the working of the one God, who made all things, and whose power controls all things. Strength or force shows itself only while it is working. Yet there was a force that was in the rock before Johnnie tried to change its place, and that stayed with it all the time it was moving and when it stopped. What force was that? The force that held it to the earth. Its name is gravitation. XXII. WORKERS THAT DO NOT GET TIRED set the muscles in the arms at work, and nearly all the muscles in Johnnie's body helped. No wonder he got tired. When he lay down, some other hidden workers. took Johnnie in hand, and in a few minutes he was ready for more work. This is the way men work everywhere with the mind and the will, using their ser vants, the muscles, and telling them where to use strength, and how much is needed. This is the way the horse, the mule, the ox, the camel, and the reindeer work for us, getting tired and resting. WORKERS THAT DO NOT GET TIRED 49 A little plant growing in a crevice in a great rock has been known to break it open to make room to grow. Let us think now of other kinds of force, such as do not get tired and have to stop and rest to get new strength. Out yonder water is falling over the rocks. Is there any force there? The boy is going to throw in a dead branch broken from a tree. What is the water going to do about it? A hundred times as much force as the little boy used to move the rock is being used every minute. The boy could work a few minutes; the men or the horse could work a few hours at a time; that little brook works all the year around. After men had seen that strength run to waste year after year it came into their minds to harness it to a great mill wheel, as a horse is harnessed to a plow. So, a little way down before the stream was to spread out to make a pond and cover a little valley, they built a mill and used the strength the water had laid up in its course to saw trunks of trees into planks and boards. Elsewhere a great pond held water which was using its strength only in standing still. Men found out a way to raise some of it to the top of a high hill close by. W They called upon the wind to help them do this, and the way they spoke to the wind was by building another kind of mill with great fans. Men who had been toiling with oars to overcome the strength of wind and water in crossing lakes and streams, or in going out upon the sea, found still another way to save their own strength and use something that would not get tired. They made a sail of cloth, and the boatman by ropes or cords in his hand turned it to catch the breeze. The picture shows a ship fully rigged with sails and ropes and spars. |