Supplement No. 12, corrections and additions to Bulletin No. 18 to supplement information given upon charts of Great Lakes, and issued with those charts from Office U.S. Lake Survey, Detroit, Mich. : Great Lakes, their harbors, channels, and navigable tributaries
Includes cumulative index to Supplements No. 1-12 to Bulletin No. 18.
Reports include description of lake waters, tributaries, shores, navigation dangers, weather, and bridges, with occasional data; navigation seasons; sailing directions; marine rules and regulations; Survey chart references and updates; results of dredging and other improvement activity; and lists of U.S. life-saving stations, and U.S. Weather Bureau and Canadian storm-warning display stations.