The Louisville and Nashville Railroad Company is hereby required to establish and maintain, at its own expense a watchman from 6:00 a.m. to 6:00 p.m., where Dunlap Street and Poplar Street cross said railway and from 6:00 a.m. until 10:00 p.m., where Rison Street and Depot Street across said railway; subject nevertheless, to the substitution of an electrical device in lieu thereof as hereafter provided.