It shall be the duty of all persons, corporations, companies, or any other person or persons whatever, having or owning, or who may hereafter have or own any bridge, or aqueduct, or any other structure spanning the Allegheny river, and resting upon piers or other support in said river, at any point or place thereon between its confluence with the Monongahela river and Warren, Warren county, Pennsylvania, to keep a light or lights burning on each pier, at all hours of the night, when the said river is in navigable stage for boats or rafts, so that said light or lights may be readily seen by persons descending said river, at all hours between dark in the evening and daylight in the morning.