All sales or leases made prior to the year 1860 by the county court, or court of monthly session, of any county of any land or building then owned by such county and situated within the limits of land previously acquired by such county as a site for its courthouse and other public buildings, when the consideration therefor has been fully paid and the purchaser, or lessee as the case may be, and those claiming through or under him, shall have held continuous possession of such land or building from January 1, 1860, until January 1, 1934, are hereby validated and declared to be forever binding upon such county.