"Perhaps we can make Norah tell herself all about it, Will," said Fred. "You remember what a heavy rain we had last night, Norah?""Oh yes," said Norah, "the water stood in great puddles in the road.""Where are the puddles now?"
"They are all gone; the water has sunk down into the earth." said Norah.
"Why does the water sink into the earth?" "Because the earth is porous and absorbs it," saidNorah.
"Quite right," said Fred. "But is all earth porous?"" "No. Clay is not porous." said his sister.
