Good Riddles

Question: 100 feet in the air, yet its back is on the ground.

What is it?

Question: Who was buried in Grant's Tomb?

Question: A truck driver is going opposite traffic on a one-way street. A police officer sees him but doesn't stop him.Why didn't the police officer stop him?

Question: You have a glass of water that looks about half full. How can you tell, only using the glass of water itself, if the glass is half full or not?

The glass is a right cylinder.

Question: There is a 5 gallon and a 3 gallon box. You also have a hose with unlimited water. How are you gonna make the 5 gallon have 4 gallons using your items? (You do not know the exact measure measurements of a gallon)