ABSENT-MINDED

Dr. Harold C. Urey, Nobel prize winner in Chemistry, was walking along a sidewalk one day when he ran into another professor. They chatted for a few minutes, then, as they parted, Dr. Urey asked the other: "John, which way was I going when I met you?" "That way," said the other, pointing. "Oh, good. That means I've already had my lunch," muttered the professor as he walked away. 

Bits & Pieces, August, 1989.