"Rolling" a map color form on a flat bed press. The plates pictured here have been made by the wax engraving process. In many cases only a portion of a map is corrected. This portion or "patch," as it is called, is made by this process and when completed is inserted into the existing map plate, thus bringing the map up to date.

Wide World Photos, Inc. · [ca. December 1938]

[Information from item housing] Maps & Mapmaking