5. What is the stream, and what is the force pump that forces the stream on?
6. What are the rules for keeping the little freight boats, and the great Dreadnoughts on this wonderful stream in the best working condition?
TWO MILLS
Come, children, listen to the story Uncle Ned told to me. It was the story of a long time ago when Uncle Ned was a little boy. One day his mother took him on her knee and said, "Ned, do you know that your mouth is like a little mill?" It is. The mill grinds corn. Your teeth grind your food. Look in the mirror. Are your teeth all alike? Some of the teeth in your mouth are to bite the food into bits, and others are to grind it fine so that it will not hurt your stomach.
You have twenty now because you are a little boy and do not need any more. When you have grown to be a man you will have thirty-two teeth. You will have more grinders in your mouth when you are a man than you have now. The jaw teeth are called grinders, because they grind the food you put into your mouth, just as the big mill stones grind the corn into meal down at Grandpa's mill.
You wear clothes to keep your bodies warm, so the teeth need some covering to keep out the cold. The enamel, a hard outer covering on the teeth, keeps them from feeling the cold. Down in the middle of the tooth is a place for the nerves of the tooth. When you break the covering on the tooth the cold and hot things that you sometimes put into your mouth will make the nerves ache. Sometimes things that are very sweet or very sour hurt the covering on the teeth.
To use the teeth to crack nuts or ice will harm them, for it often breaks the outer covering, and it will not grow again.
Your teeth should last you all your life if you will take care of them. Grandpa's mill would not grind the corn well, nor would the mill last long, if he did not take care of it and keep the big stone grinders clean and free from grit and dirt. Your teeth must have just as good care as the stones in the mill if you wish them to last you a long time, and if you want them to grind your food fine.
This is why you must use your toothbrush, and wash your mouth out regularly every day. If you do not keep your mouth clean, germs will creep in and cause the little boy to have toothache. You are wondering what the germs have to do with toothache.