It shall be the duty of every person hereafter becoming a holder of unseated lands, by gift, grant or other conveyance, to furnish to the county commissioners, or board for the assessment and revision of taxes, as the case may be, a statement signed by such holder, or his, her, or their agent, containing a description of each tract so acquired, the name of the person or persons to whom the original title from the Commonwealth passed, and the nature, number and date of such original title, together with the date of the conveyance to such holder, and the name of the grantor, within one year from and after such conveyance, and on failure of any holder of unseated lands to comply with the injunctions of this act, it shall be the duty of the county commissioners to assess on every tract of land, respecting which such default shall be made when discovered, four times the amount of the tax to which such tract or tracts of land would have been otherwise liable, and to enforce the collection thereof, in the same manner that taxes due on unseated lands are or may be assessed and collected: Provided, That nothing in this section shall be construed as giving greater validity to unexecuted land warrants than they are now entitled to, nor to the detriment of persons under legal disabilities, provided such person or persons comply with the foregoing requisitions within the time or times limited, respectively, after such disability shall be removed.