During a beach walk along Croton Point's north shore, the author discovered old bricks embedded in concrete, stamped with "IX" and "XL" markings. These artifacts originated from William A. Underhill's brickyard at the point's northern end. The bricks bore the "IXL" stamp, representing a marketing strategy meaning "I excel" at brickmaking. Some displayed Underhill's initials (WAU) instead. The bur…