The adoption of a budget shall not be construed as authority to any officer of the City to expend the amount set forth in such budget unless such expenditure has been authorized by proper warrant.
At any meeting after the adoption of the budget and after at least one week's notice to the members of the Council, the Council may amend such budget so as to authorize the transfer of unused balances appropriated for one purpose to another purpose, or to appropriate available revenues of a class not included in the annual budget.