Children. A soft substance.
Teacher. Is there any other sort of wax that is not soft?
Children. Yes, the whacks you give us when we don't know our lessons.
Teacher. What does a cow give us?
Children. Nothing.
Teacher. Well, what does the milkman give us?
Children. He gives us nothing; we buy it.
Teacher. What do we buy from him?
Children. Milk and water.
Teacher. What's this?