If, at any time after the disincorporation of said city, it shall be found that there is not sufficient money in the treasury to the credit of the fund, herein above provided, with which to pay any indebtedness of said corporation, the board of county commissioners of said county shall have the power, and it shall be their duty to levy, and there shall be collected from the territory formerly included within said city, a tax or taxes sufficient in amount to pay the indebtedness of said corporation as the same shall become due. Such tax or taxes, assessments and collections shall be made in the same manner and at the same time that other taxes of the said county are levied and collected and shall be an additional tax upon the property included within said territory for the payment of said debts.