What did chillingworth find on dimmesdale's chest?

He finds a scar in the shape of an "A" on his chest. You really aren't supposed to find this out until later in the book. It gets revealed in the end of the book. I can't remember the entire book, but if I remember correctly somewhere toward the end of the book, Hester and Dimmesdale both stand on a scaffold with their "A" showing.