The authority delegated both to counties and to municipalities represents a part of the State sovereignty. Scales v. Ordinary of Chattahoochee County, 41 Ga. 225, 226; 7 R. C. L. 923, § 2; 19 R. C. L. 691, § 4. While at common law counties exercised functions pertaining only to their sovereignty, and therefore acted in a governmental capacity, with the result that they 'were held to be immune from suit (County of Monroe v. Flynt, 80 Ga. 489, 490,
