All public bridges within a city of the first class, exceeding sixty feet in length, and the approaches thereto, over any stream crossing a county highway, shall be constructed and kept in repair by the county. When any city of the first class has constructed or repaired a bridge over sixty-feet span with approaches thereto, on any county highway within its corporate limits, and has incurred a debt for the same, then the treasurer of the county in which such bridge is located shall pay to the city treasurer seventy-five percent of all bridge taxes collected in such city until such debt and interest upon the same are fully paid. The city council may appropriate a sum not exceeding five dollars per linear foot to aid in the construction of any county bridge within the limits of such city, or may appropriate a like sum to aid in the construction of any bridge contiguous to such city on a highway leading to such bridge.