Maine granite slates Silurian Montalban rocks geology railroads c.1890 color mapGeological Map of Maine Colored to show the Geological Formations By Prof. C. H. Hitchcork (Maine early Geology map) Issued c. 1890 1900 likely by Stuart & Colby. Lovely late 19th century antique lithographed map with original hand color. Color coded key bottom center includes nine different geological designations, including granite, trap and altered slates, upper ilurian, etc. Map further identifies numerous railroad routes, which weave through the