To determine the original width of the windows, the header arches and lintels were recorded and then the windows were examined to determine if one side of the jamb survived.  Once a surviving jamb was found, the center of the ca. 1797 lintel or arch was marked and a measurement was taken to find the distance between the center of the arch or lintel and the jamb.  This measurement was then doubled to determine the original width of the ca. 1797 rough openings.