user: Question: When was successor George E. Harris (R) seated?
Columns: ['District', 'Vacator', 'Reason for change', 'Successor', 'Date successor seated']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['Virginia 2nd', 'Vacant', 'Virginia re-admitted into the Union', 'James H. Platt, Jr. (R)', 'January 26, 1870']
SQL:

assistant: SELECT "Date successor seated" FROM "Table" WHERE "Successor" = 'George E. Harris (R)';