CREATE TABLE table_26650 ("State  ( class ) " TEXT, "Vacator" TEXT, "Reason for change" TEXT, "Successor" TEXT, "Date of successors formal installation" TEXT)

List the number of vacators when successors were formally installed on June 22, 1868.
SELECT COUNT("Vacator") FROM table_26650 WHERE "Date of successors formal installation" = 'June 22, 1868'
SELECT COUNT("Vacator") FROM "table_26650" WHERE "Date of successors formal installation" = 'June 22, 1868'