Sec[Section] 1^st Be it enacted by the people of the State of Illinois represented in the General Assembly, That Spoon River be and the same is hereby declared a navigable Stream from its confluence with the Illinois River, up to Cameron’s Mill on said River, and the Same Shall at all times hereafter be a public highway, and free for the passage of boats and water crafts from the mouth of Said River up to Said mill, Provided that any person or person wishing to build a mill dam on said river, may do so by constructing an apron to such mill dam so as to permit flat and keel boats to pass the Same. This act to take effect, and be in force from and after the first day of June next,