County authorities shall never assess taxes, in any one year, the aggregate of which shall exceed ninety-five cents per one hundred dollars valuation, except for the support of free schools; payment of indebtedness existing at the time of the adoption of this Constitution; and for the payment of any indebtedness with the interest thereon, created under the succeeding section, unless such assessment, with all questions involving the increase of such aggregate, shall have been submitted to the vote of the people of the county, and have received three fifths of a ll the votes cast for and against it.