Graham, J. D. (James Duncan), 1799-1865Mayer, J. R. (John R.)United States. Army. Corps of Topographical Engineers1 map ; 51 x 70 cm"Soundings are in feet and tenths of a foot.""The figures on land express the elevations above the lake surface in feet and decimals. The horizontal curves or contour lines are drawn at intervals of 5 feet of perpendicular elevation.""Accompanying Lt. Colonel Graham's annual report (no. 200) to the Chief Top. Engineer, dated Chicago September 30th 1857.""Map G no. 50."JPEGG 4114 .S65P55 1857 .M600155226739015091897309engPublicMouth of South Black River, MichiganMapsBlack River1856-1857University of Michigan