bu. for bushel or bushels. c. c. for cubic centimeter. cm. for centimeter. cwt. for hundredweight. dwt. or pwt. for pennyweight oz. for ounce or ounces. etc. (not &c.) for et cetera. ft. for foot or feet. H. m. s. for hours, minutes, and seconds. (Use capital H.) in. for inch or inches. kw. for kilowatt or kilowatts. £ s. d. for pounds, shillings, and pence. per cent (omitting period) for per centum. Spell out percentage. ser. for series. St. for Saint or street U. S. Army for United States Army, as distinguished from United States of America (U. S. A.). yd., yds. for yard, yards. [Illustration: U. S. GEOLOGICAL SURVEY PREPARATION OF ILLUSTRATIONS PLATE VI 175-LINE SCREEN 150-LINE SCREEN 133-LINE SCREEN 120-LINE SCREEN 100-LINE SCREEN 65-LINE SCREEN HALF-TONE CUTS SHOWING EFFECT OF SEVERAL STANDARD SCREENS IN THE REPRODUCTION OF THE SAME DETAIL.] The names of certain months may in some places be abbreviated; those of others should invariably be spelled out. The following are the correct forms: Jan. Apr. July Oct. Feb. May Aug. Nov. Mar. June Sept Dec. The abbreviations for number and numbers before figures are No. and Nos. The o should never be raised, as in N^o. The abbreviation for Mac is Mc, not M^c. All periods should be omitted from abbreviations used in the body of a map unless their omission would cause misunderstanding. They are generally unnecessary, and if used on some maps they are likely to be mistaken for symbols representing certain features, such as houses or flowing wells, if either is shown. Periods used on drawings that are to be reproduced "direct" or photomechanically should always be slightly exaggerated. NAMES OF RAILROADS. The names of railroads may be written in full or abbreviated, in accordance with the kind of map and the space available. On a sketch map in black and white the initial letters are generally sufficient. On a more detailed map, if there is room enough, the names may be spelled out. As already stated, neither the words "railroad" and "railway" nor the abbreviations R. R. and Ry. should be used on a map. MAKE-UP OF MAPS. FORMS FOR CERTAIN FEATURES. The proper forms for certain features of maps, such as the borders, titles, explanations, bar scales, captions, arrows indicating true north and magnetic declination, source, and authorship, are shown in Plate VII. Note particularly the style and position of the marginal matter. BORDER.