Logic Riddles

Question: I sit on a bridge so you might see just how clear the world can be. What am I?

Question: There are three books on a shelf standing side by side. Each book is 10ml thick. The bookworm eats its way through the first page of the first book to the last page of the last book. How far did the bookworm move if it can only move in a straight horizontal line?

Question: In the books of a famous writter, How many letter in Those Books?

Question: Does an ounce of gold or an ounce of feathers weight more?

Question: Something you know nobody knows, and everyone knows something you don't. We all know something, nobody knows everything, and you know something someone doesn't know. What else could nobody know?