"All these things-sponge, charcoal, and sand- are porous. We have a filter now, ready for use. Butas I have some charcoal and sand left, I will put two more layers in.
"Now if we pour any dirty muddy water into the top of the flowerpot, we shall see it trickle through the bottom clear and bright."SUMMARY
The earth is a great ?lter. It allows the clear spring water totrickle through its pores, but keeps back all the mud.
Lesson 06
Soluble
"We had another lesson today," said Fred, "about things which dissolve and things which melt.""Let me join you for a few minutes," said his father, "I have here some loaf-sugar broken up fine. I will put some of it into this tumbler of water; the rest into this iron spoon. Fred shall stir the water in the tumbler. I will hold the spoon over the fire. Now watch. I think we can make it all clear.
"Look," he went on, "the pieces of solid sugar in the spoon are changing into liquid sugar. We can see it flow about in the spoon. This sugar is melted.