According to value. Duties are either ad valorem or specific; the former when the duty is laid in the form of a percentage on the value of the property ; the latter where it is imposed as a fixed sum on each article of a class without regard to its value. The term ad valorem tax is as well defined and fixed as any other used in political economy or legislation, and simply means a tax or duty upon the value of the article or thing subject to taxation. Bailey v. Fuqua, 24 Miss. 501; Piugree v. Auditor General, 120 Mich. 95, 78 N. W. 1025, 44 L. It. A. 079.