Then make the proper divisions and subdivisions of the country: and having the latitudes and longitudes of the prin cipal places, it will be easy to set them down in the map : for any town, Ste. must be placed where the circles of its latitude and longitude intersect. For instance, Gibraltar, whose latitude is 36° 11", and longitude 12° 27', will be at G : and Ma drid, whose latitude is 40° 10', and longi tude 14° 44', will be at M. In like man ner, the mouth of a river must be set down ; but to describe the whole river, the latitude and longitude of every turn ing must be marked down, and the towns and bridges by which it passes. And so tor woods, threats, mountains, lakes, cas tles, &c. The boundaries will be de scribed by setting down the remarkable places on the sea-coast, and drawing a continued line through them all. And this way is very proper for. small coun tries.
Secondly. Maps of particular places are but portions of the globe, and there thre may be drawn after the same man ner as the whole is drawn. That is, such a map may be drawn either by the ortho graphic or stereographic projection of the sphere, as in the last problem. But in partial maps, an easier way is as fid lows : having drawn the meridian A B (fig. 3.), and divided it into equal parts as in the last method, through all the points of division draw lines perpendicu lar to A B, for the parallels of latitude; CD, E I', being the extreme parallel. Then to divide these, set off the degrees in each parallel, diminished after the manner directed for the two extreme parallels C D, E F, in the last method : and through all the corresponding points draw the meridians, which will be curve lines ; which were right lines in the last method; because only the extreme paral lels were divided by the table. This method is proper fb• a large tract, as Europe, &c. ; in which case the parallels and meridians need only be drawn to every 5 or 10 degrees. This method is much used in drawing maps, as all the parts are nearly of their due magnitude, but a little distorted towards the outside, from the oblique intersections of the meri dians and parallels.
Thirdly. Draw P B of a convenient length, fin- a meridian ; divide it into 9 equal parts, and through the points of division describe as many circles for the parallels of latitude, from the centre P, which represents the pole. Suppose AB
(lig. 4.) the height of the map, then C D will be the parallel passing through the greatest latitude, and E F will represent the equator. Divide the equator E Pinto equal parts, of the same size as those in A B, both ways, beginning at B. Divide also all the parallels into the same num. ber of equal parts, but lesser in propor tion to the numbers for the several lati tudes, as directed in the last method for the rectilineal parallels. Then through all the corresponding divisions draw curve lines, which will represent the meridians, the extreme ones being EC and FD. Lastly, number the degrees of latitude and longitude, and place a scale of equal parts, either of miles or degrees, for mea suring distances. This is a very good way of drawing large maps, and is called the globular projection ; all the parts of the earth being represented nearly of their due magnitude, excepting that they are a little distorted on the outsides.
Finally. • To draw a map of Europe, which extends from 36° to 72° north lati tude : draw a base line (fig. 5.) G II, in the middle of which erect a perpendicu lar, 1 l', and assume any distance for 10° of latitude. Let the point I be 30., from which set off six of the assumed distances to P, which will be the north pole. Number the distances 40, 50, 60, &c. and on the centre, P, describe arcs pass ing through the points of divisions on the line I which will be parallels of latitude. Divide the space assumed for 10° of latitude into 60 parts, by some diagonal scale. Look into the table, Art. LONGITUDE, for the number of miles an swering to 30°, which is 51.96; take this from the scale, and set it off on the arc 30° from the centre line both ways. Do the same for 40°, 50°, 60°, &c. and through the corresponding divisions on all the arc§ draw curve lines ; which will represent the meridian. When the de grees of latitude and longitude are marked the thing is done.
When the place is but small that a map is to be made of, as if a country were to be exhibited ; the meridians, as to sense, will be parallel to one another, and the whole will differ very little from a plane. Such a map will be made more easily than by the preceding rules. It will here be sufficient to measure the distances of places in miles, and so lay them down in a plane rectangular map.