Coast and Geodetic Survey, United States, 13 Coast pilots, 154 Compass bearings, 130 Compass, nautical use of, 6 Compass, variation of, 7 Compilation of information, 67 Correction of charts, method of, 110 Cosa, Juan de la, 8 Current charts, 157 Currents, 50, 121 Danger angle, horizontal, 136 Danger bearing, 131 Danger range, 132 Dangers, reports of, 56 Dates on charts, 123 Dead reckoning, 129 Depth curves, 116, 152 Depths, unit for, 19, 116 Depth units, relation of, 118 Directions on charts, 115 Distances, measured on chart, 125 Distribution of charts, 96 Doubling angle on bow, 131 Draft of vessels, 97 Dragging for dangers, 55 Earthquakes, 109 Electrotyping plates, 89 Elevations, 122 Engraving machines, 89 Engraving on copper, 84 Engraving on stone, 93 Eskimo map, 1 Etching on copper, 95 Explanatory sheets, 159 Flattening of the earth, 3 France, establishment of chart office, 10 Geographic position on charts, 115 Geography, early, 2 Germany, contributions to hydrography, 14 Gnomonic charts, 79, 157 Gnomonic projection, 74 Great Britain, contributions to geography, 14 Holland, development of chart making, 10 Hydrographic Office, British, 13 Hydrographic Office, United States, 13 Hydrography, 40 Index charts, 158 Information on charts, 23 Instruments used on charts, 141 Lake Survey, United States, 13 Largest scale chart, 151 Latest editions of charts, 148 Light and buoy lists, 156 Lithographic printing, 94 Locating a vessel, 126 Longitude, initial, 19 Longitude, uncertainties in, 10 Magnetic charts, 157 Magnetic variation, 56 Map, earliest, 2 Map making, development of, 2 Maps, need of, 1 Maritime surveys, extension of, 17 Mercator chart, history, 8 Mercator projection, 68 Meteorological charts (pilot charts), 158 Navigation, use of charts in, 124 Notices to mariners, 111, 155 Paper, shrinkage of, 152 Parallel rulers, Field's, 141 Photolithography, 93 Plane of reference, 20, 119 Plotting positions, 124 Polyconic projection, 73 Printing, plate, 84, 90 Privately published charts, 21 Progress of hydrographic surveys, 17 Projection, explanation of, 114 Projections, 68, 114 Protractor, three-arm, 144 Ptolemy, 3 Publication of charts, methods, 84 Purpose of charts, 22 Ranges, 132 Reading charts, 112 Reliance on charts, 144 Reports of dangers, erroneous, 57 Requirements for charts, 23 Revision of charts, need of, 97 Rock, Brooklyn, 50 Sailing directions, early, 4 Sailing directions, 154 Scale equivalents, 113 Scales of charts, 79, 112 Set, graphical allowance for, 125 Sextant angles, 132 Sheets for surveys, 39 Shrinkage of paper, 152 Sound, position by, 140 Sounding machines, 49 Soundings, position by, 136 Star charts, 159