Through the points thus obtained on the central meridian draw lines at right angles to the vertical line. Along these horizontal lines lay off the dimensions in the column headed X, Table 6 (pp. 39-47) of "Geographic tables and formulas" as required for each individual map--in the diagram every alternate degree. Draw vertical lines at these points and set off the distance Y in the same table in a similar manner, and the points so found will be the points of intersection of the respective meridians and parallels. Figures are given on the diagram for the thirty-fifth parallel only. DETAILS OF BASE MAPS. Anyone who attempts to draw a base map must, first of all, know how each feature or part of the map should be represented. Most of the conventional symbols for features shown on base maps are well established and should invariably be used; for instance, a line composed of alternate long and short dashes (not dashes and dots) represents a county boundary, and a line or two parallel lines across which short lines are drawn at regular intervals represents a railroad. If he finds that two or more symbols have been widely used to represent the same feature the draftsman should select the one that is best suited to the map in hand. The correct forms of the conventional symbols or features to be used in preparing miscellaneous maps are shown in Plate IV, but the size and weight of each line or symbol must depend on the size and character of the map. TRANSFERRING OF COPYING. TRACING. The oldest method of transferring a map or parts of a map or other drawing to another sheet is that of copying it by means of tracing paper. This method, though still used for simple work, has given way to quicker and more effective methods. By one of these methods a piece of thin, fairly smooth paper (not necessarily transparent) is coated with graphite by rubbing over it a soft pencil. When the graphite has been evenly distributed over it, this sheet is laid upon the drawing paper, coated side down, the map or other subject to be copied is laid upon the graphite-coated sheet, and the two outer sheets--the drawing paper and the map--are securely fastened together. By a steel tracing point or very hard pencil the lines and other details of the matter to be copied are then firmly and carefully traced and thus transferred to the clean drawing paper beneath.