THATthe letters patent granted to Timothy P. Anderson, a citizen of the United States, on the twenty third day of December, eighteen hundred and thirty three, for his improvement in the economy of water power, by means of a graduated spout or trough, be, and the same are hereby, extended for the term of seven years, from the passage of this act, to the widow of said Timothy, deceased, and his heirs at law, for their joint and sole use; and the commissioner of Patents is hereby required, upon the surrender of said patent and the payment of the fees and charges provided for by law, to issue to the said widow and heirs a patent for their benefit, reciting therein the said first named patent, and also referring to this act: Provided, however, And such new patent shall be open to legal inquiry and decision in the same manner as if issued under the general law regulating the granting of patents: And provided, further, That all persons now enjoying the lawful use of said graduated spout, and the purchaser of any such spout may continue to use the same notwithstanding the provisions of this act.