Except as herein otherwise provided, no money shall be paid out of the City Treasury except upon warrant, signed by the Mayor and approved by the Board of Aldermen, such approval to be authenticated by the City Clerk. A full record of all expenditures shall be kept, and a clear statement of all receipts and disbursements of City moneys, and of the affairs of the City generally, shall be annually published under the direction of the City Council, at least two weeks before the annual City election. No City official shall be directly or indirectly interested in any contract with the City.