The 1851 census page is quite faint and is difficult to read. Port Iron (Rushen) HO1078/2526 entry 114
David Watt Head Widower 80 Beggar (Ag. Lab.) b. Ireland
Ann Watt Daughter 28 Unmarried b. Rushen
Henry Watterson grandson 3 b. Rushen.
Ancestry.com has transcribed Watt as Wall.
Henry was christened Hanry Watt mother Ann Watt on January 2 1848 in Rushen