A finished map border is used or omitted according to the kind of map prepared. Diagrammatic maps and maps on which no parallels and meridians appear do not need finished borders. On a map that shows complete areal geologic or other coloring, such as a map in a Survey geologic folio, the border lines tend to destroy the simple effect of the whole map. On a map that is not completely colored and on all very large maps borders are really necessary. If borders are used, however, the space between the neat line and the outer line of the border should be only sufficient to provide proper space for the numbers showing latitude and longitude or township and range. A simple rule[8] for determining the width of this space is as follows: Divide the sum of the dimensions of the map by 2 and find the square root of the quotient, which will represent the width of the border in sixteenths of an inch. Example: Map is 20 by 30 inches; (20 + 30)/2 = 25; square root of 25 = 5; width of border = 5/16 inch. [Footnote 8: Worked out by Martin Solem, of the U. S. Geological Survey.] The numbers showing latitude and longitude should be in shaded arabic numerals and those showing township and range in gothic. The symbols for degree, minute, and second should not be crowded. On a map that has no added border lines the numbers should be in hair-line gothic. TITLE. The title of a map should be in roman letters and if placed at the lower margin should generally be arranged in two lines, unless it is short. If it forms two or more lines the lines should be well balanced. The first line should describe the position of the area; the second line should state the purpose of the map, as MAP OF BUTTE AND VICINITY, MONTANA SHOWING LOCATION OF MINES AND PROSPECTS. A title placed inside the border of a map should be arranged in a series of lines, generally beginning with "Map of" or "Geologic map of." and the line showing the dominant part of the title should be emphasized by larger lettering, thus: =MAP OF= THE VICINITY OF BUTTE MONTANA SHOWING LOCATION OF MINES AND PROSPECTS. The name of the author or compiler of a map or of the person supplying the geologic or other data shown on it may be placed either beneath the title or in the lower right corner, just below the border line, and the names of the topographers or the source of the base should be stated in the lower left corner, just below the border line. If the title is placed inside the border all notes giving credit for any part or features of the map may be placed beneath the title or scale. (See PI. VII.) [Illustration: U. S. GEOLOGICAL SURVEY PREPARATION OF ILLUSTRATIONS PLATE VII DETAILS OF THE MAKE-UP OF A GEOLOGIC MAP] EXPLANATION.