Other magnetic charts are published showing the lines of equal magnetic dip, horizontal magnetic force, and vertical magnetic force. #Meteorological ocean charts# are published by several governments, including the United States, Great Britain, and Germany, and give the average weather conditions, winds, fogs, currents, ice, tracks of storms, and other information. "Pilot charts" of the North Atlantic and North Pacific Oceans are issued by the United States Hydrographic Office about the first of each month, and give "a forecast of the weather for the ensuing and a review of that for the preceding month, together with all obtainable information as to the most available sailing and steam routes, dangers to navigation, ice, fog, derelicts, etc., and any additional information that may be received of value to navigation." Mariners in all parts of the world have joined in contributing the information which has been used in compiling these pilot charts. #Track charts# are published by the British and United States governments. That of the latter is entitled "Track and distance chart of the world, showing the routes traversed by full-powered steamers between the principal ports of the world, and the corresponding distances." #Telegraph charts# are published showing the "telegraphic connections afforded by the submarine cables and the principal overland telegraph lines." #Index charts# are outline plans showing the area covered by each chart of a series, and furnish a convenient means of finding a chart of any desired region or of selecting the most suitable chart for any purpose. These index charts are published either in sets, showing all the charts of a series, or are bound into the chart catalogues. #Star charts# are included in navigational series, and are conveniently arranged for use on shipboard in identifying the brighter stars. The United States Hydrographic Office publishes two, constellations of the northern and of the southern hemispheres. #Explanatory sheets# are published in connection with various series of charts, giving explanations of the symbols and abbreviations used and of other important features. In the United States the Coast and Geodetic Survey has issued a small pamphlet, "Notes on the use of charts," which contains explanations of its chart symbols, and the Hydrographic Office has published "A manual of conventional symbols and abbreviations in use on the official charts of the principal maritime nations." INDEX PAGE Aids to navigation, 118 Arbitrary projection, 79 Astronomical observations, 32 Astronomical positions, 126 Bearings, position by, 130 Board of Trade notice, 148 Care of charts, 153 Catalogues of charts, 157 Changes in the coast, 98 Chart making, development of, 6 Chart publications of various nations, 18 Charts, earliest nautical, 6 Charts, loxodromic, 7 Charts, plain, 8 Chart schemes, 67 Chart working, 124