Premier Sir Charles Cowper (1807-1875) KCMG left office 2 October 1856, when did he assume office?
CREATE TABLE "historical_premiers" (
  "rank" real,
  "state" text,
  "premier" text,
  "party" text,
  "assumed_office" text,
  "left_office" text,
  "total_time_in_office" text
);
SELECT "assumed_office" FROM "historical_premiers" WHERE "premier"='sir charles cowper (1807-1875) kcmg' AND "left_office"='2 october 1856';