Section 16. The directors, before fixing the route of the railroad as hereinafter provided, shall publish a copy of the agreement of association in a newspaper, if any, published in each of the cities and towns where the railroad is to be located, and if, in any county, a newspaper is published in none of said cities and towns therein, in such newspaper published in said county as shall be designated by the department, at least once in each of three successive weeks; and, three weeks before fixing said route, shall also post a copy of said agreement in two or more public places in each of said cities and towns where said railroad is to be located; and the sworn certificate of the clerk shall be conclusive evidence of such publication and posting.