CHART, a representation of a portion of the earth's surface projected on a plane. The term is commonly restricted to those intended for navigators' use, on which merely the out lines of coasts, islands, etc., are represented.
A globular chart is a chart constructed on globular projection. Mercator's chart is a chart on the projection of Mercator. A plane chart is a representation of some part of the superficies of the earth, in which the spherical form is disregarded, the meridians are drawn parallel, the parallels of latitude at equal dis tances and the degrees of latitude and longi tude equal. A selenographical chart is a chart representing the surface of the moon; and a topographical chart is a chart of a particular place, or of a small part of the earth.
Charts are designed to assist the navigator and to subserve the interests of commerce. For purposes of navigation they may embrace large areas, like one of the great oceans or seas, delineating the conformation of the shores and outlying dangers, and perhaps indicating the principal currents and winds that may be util ized in determining the most advantageous 'routes between specified localities. Charts may also embrade much smaller areas, but on larger scales, permitting greater fullness of detail, and thus presenting graphically the channels that can be followed, with the depths of water, the position of lights, beacons, spindles, buoys and other objects provided to indicate the way to the stranger. Charts of these classes are usu ally designated °Navigation charts,* although they may also be useful for other purposes.
Nearly all civilized nations have published charts of their coast lines in greater or less detail, and the principal maritime nations copy those issued by other nations, and thus maintain for the use of their own seamen charts of all parts of the world to which their commerce may extend. Great Britain maintains the most extensive establishment for the purpose, and issues the most complete series of charts; she has also made the most extensive surveys of unsettled coasts for cartographic purposes.
The United States Coast Survey, a vast un dertaking, was begun in 1807, carried on inter mittently till 1845, and since then more system atically, save during the Civil War, under Professor Bache, Professor Pierce and their successors. The coasts of the United States are surveyed and the charts produced by the Coast and Geodetic Survey attached to the Treasury Department, which also makes re searches to determine the origin and courses of the Gulf Stream 0.v.). Unsurveyed foreign coasts and the Great Lakes are surveyed by the Bureau of Navigation, the charts being pro duced by the Hydrographic Office of the Navy Department. This bureau also duplicates charts and plans issued by other nations. The Coast and Geodetic charts are sold at from 10 cents to $1 each, being the cost of printing and paper. Naval vessels are supplied free. The charts are obtainable at Coast and Geodetic Survey agencies at all seaports of the United States. They exhibit accurate and minute topography as far inland as will supply land marks for the navigator or serve for purposes of defense; the shore line at high water, and sanding to mean low water; soundings, con tours and material of bottom at different depths; bars, channels, sailing ranges and di rections; true meridian and compass variation; rocks, reefs, buoys, beacons, lights; tide estab lishment; detailed explanation of lighthouses and signal stations. They are carefully cor
rected for every substantial change in any of those features. They range in scale from (30.401 inches to the nautical mile) to of an inch to the nautical mile). The Coast and Geodetic Survey issues four series of charts on the Atlantic and Gulf coasts of the United States, and three series on the Pacific Coast, designed to subserve the purposes the surveys were established to meet. The first series includes °sailing charts," which embrace long stretches of coast, as from the Bay of Fundy to Cape Hatteras, Chesapeake Bay to the Bahamas, etc., and are intended to serve for offshore navigation, or between the greater headlands, as Cape Cod, Cape Hatteras, etc., and between distant harbors, as Boston to Chesapeake Bay, Charleston, etc. They show only the outline of the continent, the seacoast lights and geographic information that will be useful for the purposes intended. The second series includes °general charts of the coast,* also designed for purposes of navigation. They are on a scale three times as large as that of the first series, and embrace more limited areas, as the Gulf of Maine, Gay Head to Cape Henlo pen, Galveston to the Rio Grande, etc. These charts serve the navigator in coasting along shore between headlands, and in approaching harbors. Those of the third series, called "coast charts," embrace the whole coast on a uniform scale five times as large as that of the second series. Such charts are necessarily con fined to comparatively short stretches of coast, as Sandy. Hook to Barnegat, the entrance to Chesapeake Bay, Mobile Bay, etc. One inch on the paper represents about one and one-fourth statute miles, a scale sufficiently large, to give the features of the topography and hydrog raphy with great clearness, portraying the ap pearance of the coast and the irregularities of the bottom with a detail quite close enough for the navigation of the principal harbors. The fourth series consists of °harbor charts* on large scales, intended to meet the needs of local navigation. On the Pacific Coast the first series is similar to that on the Atlantic Coast, and extends from San Diego, Cal., to Point Barrow, Alaska. The second series is on a scale six times as large as the first, and is suit able for alongshore navigation and inland pas sages of southeast Alaska. The third series includes charts on scales like those of the fourth series on the Atlantic Coast.
All these serieS of charts are published from the same original surveys, the details of the original work being generalized or omitted to meet the requirements any particular series is intended to subserve. Various methods are available for producing charts of these classes, but experience has demonstrated that on coasts like large portions of those of the United States, which are subject to frequent changes from natural causes, necessitating ex tensive corrections, engravings upon copper are the most expedient and economical. The engravings afford the additional advantage of being readily duplicated by the electrotyping process. All the standard charts issued by the bureau are therefore copperplate engravings. Preliminary editions, however, are frequently issued by means of the photo-lithographic process, which affords a cheap and ready method for temporary purposes.
The Survey publishes about 500 charts, with an average annual issue of 70,000 copies.