"Just you try and think about the frozen ponds inwinter time, Norah. Where do we find the ice?""It covers the whole surface of the pond.""But suppose we took a hammer and broke the ice on the surface. Should we find the whole of the water in the pond solid ice?""No, the water is not frozen underneath.""Can you tell me what would become of the pieces of ice as we broke them up?""They would float on the water."
"You are quite right. Teacher put a piece of ice in the water and we saw it float on the top. But what does that prove?""It proves that the ice is lighter than the water," said Norah. "If it were heavier it would sink to the bottom.""Yes," said Fred, "ice is lighter than water, and italways forms on the surface. Even in a hard frost there is only a sheet of ice covering the surface of the water, and when it breaks up we can see the water below.
"Suppose for a moment that the ice were heavier than the water. It would sink to the bottom as it formed, and the whole pond would in time be solid ice. What would become then of the fishes and other creatures that live in the water?""Why, I suppose they would be frozen too, and die."" said Norah.