The amounts due employees of any railroad company for wages earned by services rendered to the railroad company shall constitute a lien upon the railroad and other property of the railroad company and shall be superior to the lien of any mortgage or other contract lien executed or created by the railroad company, provided that no employee shall be entitled to a lien under this Code section to an amount exceeding $500.00. (Ga. L. 1893, p. 91, § 1; Civil Code 1895, § 2329; Civil Code 1910, § 2793; Code 1933, § 94-801.)