On or before the thirteenth Tuesday preceding each primary, the Secretary of the Commonwealth shall send to the county board of each county a written notice designating all the offices for which candidates are to be nominated therein, or in any district of which such county forms a part, or in the State at large, at the ensuing primary, and for the nomination to which candidates are required to file nomination petitions in the office of the Secretary of the Commonwealth, including that of President of the United States; and shall also in said notice set forth the number of presidential electors, United States Senators, Representatives in Congress and State officers, including senators, representatives and judges of courts of record, to be elected at the succeeding November election by a vote of the electors of the State at large, or by a vote of the electors of the county, or of any district therein, or of any district of which such county forms a part.