In addition, the following shall also be a lawful fence: a fence built on good-sized, substantial posts, set firmly in the ground not more than nine feet (9′) apart. The fence shall consist of three (3) barbed wires, or three (3) planks, or three (3) slats running horizontally and fastened firmly to the posts, the first to be eighteen inches (18″) from the ground, and the second and third eighteen inches (18″) from the first and second respectively, counting from the center of each. The fence may consist entirely of wire strands, or of planks or of slats; or it may be composed of a wire, plank, and slat.