user: Question: Who was the successor that was formally installed on March 30, 1870?
Columns: ['State (class)', 'Vacator', 'Reason for change', 'Successor', 'Date of successors formal installation']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['Virginia (1)', 'Vacant', 'Virginia re-admitted to the Union', 'John F. Lewis (R)', 'January 26, 1870']
SQL:

assistant: SELECT "Successor" FROM "Table" WHERE "Date of successors formal installation" = 'March 30, 1870';