When any monument has been or shall hereafter be erected to the memory of our Confederate dead or to perpetuate the memory and virtues of our distinguished dead, if such monument is erected by the  voluntary subscription of the people and is placed on the courthouse square, the board of county commissioners of such county are permitted to expend from the public funds of the county an amount sufficient to erect a substantial iron fence around such monument in order that the same may be protected.(1905, c. 457; Rev., s. 3928; C.S., s. 6934.)