MANURE. See AcnrcutTunE.
MAP, a plane figure representing the surface of the earth, or some part of it being a projection of the globular surface of the earth, exhibiting countries, seas, rivers, mountains, cities, &c. in their due. positions, or nearly so.
Maps are either universal, or particu lar. Universal maps are such as exhibit the whole surface of the earth, or the two hemispheres. Particular, or partial maps, are those that exhibit some particular region, or part of the earth. Both kinds are usually called geographical, or land maps, as distinguished from hydrographi cal, or sea maps, which represent only the seas and sea-coasts, and are properly called charts.
Anaximander, it is said, about 400 years before Christ, first invented geographical tables, or maps. The Pentingerian tables, published by Cornelius Pentinger of Attesburgh, contain an itinerary of the whole Roman Empire ; all places, except seas, woods, and deserts, being laid down according to their measured distance's, but without any mention of latitude, longitude, or bearing.
The maps published by Ptolemy of Alexandria, A. D. 144, have meridians and parallels, the better to define and determine the situation of places, and are great improvements on the construction of maps : though Ptolemy himself owns that his maps were copied from some that were made by Manlius, Tirus, &c. with the addition of improvements of his own. But from his time till about the 14th century, during which geography and most sciences were neglected, no new maps were published. Mercator was the first of note among the moderns, and next to him Ortelius, who undertook to make a new set of maps, with the mo dern divisions of countries and names of places; for want of which, those of Ptole my were become almost useless. After Mercator, many others published maps, but for the most part they were mere copies of his. Towards the middle of the 17th century, Bleau in Holland, and San son in France, published new sets of maps, with many improvements from the travellers of those times, which were af terwards copied, with little variation, by the English, French, and Dutch; the best of these being those of Vischer and De Witt. And later observations have fur nished us with still more accurate and co pious sets of maps.
Maps are constructed by making a pro jection of the globe, either on the plane of some particular circle, or by the eye placed in some particular point, according to the rules of perspective.
In maps three things are required : first, to shew the latitude and longitude of places, which is done by drawing a certain number of meridians and parallels of latitude. Secondly, the shape of the countries must be exhibited as accurately as possible, for real accuracy cannot be obtained by any projection, because the map is on a plane surface, whereas the earth is globular. Thirdly, the bearings of places, and their distances from each other, must be shown. The projection of mall is made, as we have observed, ac cording to the rules of perspective. If the
eye be supposed to view the earth from an infinite distance, the appearance re presented on a plane, is called the ortho graphic projection. In this case, the parts about the middle are very well re presented, but the extreme parts are contracted. Geographers usually employ the Rtereographie projection, where the eye is supposed to be on the surface of the earth, and looking at the opposite hemisphere. There is likewise the globu lar projection, in which meridians, equi distant upon the surface of the earth, are represented by equidistant circles in the map. Mercator's projection is that in which both the meridians and parallels of latitude are represented by straight lines. See Own'.
In all maps the upper part is the north, the lower the south, the right hand is eastern, and the left hand western. On the right and left the degrees of latitude are marked ; and on the top and bottom the degrees of longitude are marked. When the meridians and parallels of lati tude are straight and parallel lines, the. latitude of a place is found by stretching a thread over the place, so that it may Cut the same degree of latitude on both sides the map, and that degree is the la titude of the place. To find the longi tude, stretch a thread over the place, so that it may cut the same degree of longi tude on the top and bottom, and that de gree is the longitude of the place. when the meridians and parallels of latitude are curve lines, then to find the latitude of a place, a parallel line of latitude must be drawn through it, by the same rules as the other parallels are drawn, and it cuts the sides at the degree of latitude of the place : and to find the longitude of the place, draw a circle of longitude through it, by the same rules as the other circles are drawn, and it cuts the top and bot tom at the degree of longitude of the place. We shall now proceed to show some of the most familiar constructions of maps, beginning with a general map, or map of the world, of which there are three methods : First. A map of the world must repre sent two hemispheres ; and they must both be drawn upon the plane of that cir cle which divides the two hemispheres. The first way is to project each hemi sphere upon the plane of some particular circle, by the rules of orthographic pro jection, forming two hemispheres, upon one common base or circle. When the plane of projection is that of a meridian, the maps will be the east and west hemi spheres, the other meridians will be el lipses, and the parallel circles will be right lines. Upon the plane of the equi noctial, the meridians will be right lines crossing in the centre, which will repro. present the pole, and the parallels of lati. tude will be circles having that common centre, and the maps will be the northern and southern hemispheres. The fault of this way of drawing maps is, that near the outside the circles are too near one another ; and, therefore, equal spaces on the earth are represented by very unequal spaces upon the map.