A geological map of England and Wales by George Bellas Greenough (1778-1855) appeared in three editions. The first edition’s Memoir (1820) discusses geological content but hardly mentions symbolization. Map design assumes a major role in the second Memoir (1840), where several pages advocate using area colors and patterns “to make the tints of a geological map speak to the mind as well as to the eye” (p.viii). The map’s posthumous third edition (1865), revised by a Geological Society of London committee, appeared without a text.

Between the first and second editions Greenough converted into a crusading map designer. My exploration of his papers in English libraries and archives has uncovered several probable causes: criticisms of the readability of his map, proposals for uniform geological symbols, and the need to depict newly named geological systems. Greenough’s papers record 75 information sources consulted while seeking ideas for map design. He met, corresponded with, and read the publications of artists, color scientists, color manufacturers (especially makers of watercolors), and other geologists and natural scientists.

While Greenough’s idea of matching map colors with mineralogy is geological in basis, his other suggestions stem from the theory and practice of art and color science. These include juxtaposing harmonious and contrasting colors, reserving strong colors for small areas, and coloring groups of formations brightest in the center and duller outward. He also proposes limiting the number of colors per map but varying their tone by adding black line and dot patterns to differentiate related formations.

Shifting from Greenough’s design intentions to their implementation, my use of a portable reflecting spectrophotometer and software for analyzing color on digital photographs has enabled me to measure and compare colors on copies of his maps in different library collections. Comparison of the first and second editions of his map reveals design improvements to the second edition, although hampered by his allegiance to associative color and technical problems with the black area patterns. Finally, a look at the third edition (1865) revised by a Geological Society of London committee, reveals that Greenough’s design ideas not only live on but are more successfully expressed in this map.