Keywords: Heliotrope.jpg Light reflecting from heliotrope Triangulation party of William M Scaife NOAA's http //www photolib noaa gov/cgs/index html Historic C GS Coast and Geodetic Survey Collection Image ID http //www photolib noaa gov/htmls/theb1635 htm theb1635 1922 http //www noaa gov/ US National Oceanic and Atmospheric Administration PD-USGov Triangulation Heliotrope |