Details of a geologic map, plate showing. 58 Diagrams, drawing and lettering of. 64 features of, plate showing. 64 original, general requirements for. 28-20 Director of the Survey, order by. 9 Divisions of plates and figures, serial letters and numbers for. 12 Drafting table, shadowless, description of. 47-48 shadowless, use of. 29, 48, 50 Draftsmen, detail of, to aid author. 9 detail of, to prepare base maps. 13-14 experience and reading required by. 41-42 general treatment of material by. 42-43 Drainage features, depiction of. 51-52 Drawing instruments, list of. 42 Drawing materials, kinds used. 23-26, 66-67, 69, 71 Drawings, authors', draftsmen may aid in making. 9 authors', editorial revision of. 38 finished, general requirements for. 41-42 requests for photographs of. 34 Duplicates of engravings, charges for. 38 E. Effectiveness of illustrations, elements that produce. 7, 30 Electrotypes of engravings, charges for. 38 Elements, chemical, names and symbols of. 93 Engraving on stone, process of. 89-90 _See also_ Lithography. Engravings, changes in. 38-39 original, time of keeping. 37 Erasers, injury to paper by. 67 kinds used. 25, 67-68 Erasures, smoothing paper after. 68 Explanations on maps, arrangement and lettering of. 19, 58-50 F. Figures, differences from plates. 10-11 divisions of, serial letters for. 12 methods of inserting, plate showing. 12 Formations, geologic, use of letter symbols for. 20-21 Fossils. _See_ Specimens. Four-color process, advantage of. 80 G. Gas wells, symbols for. 21 Generalization, true, meaning of. 17 Geographic tables and formulas (Bull. 650), use of. 44, 45 Geologic periods of time, names of. 92 Gouache, use of. 67, 69 Great Lakes surveys, maps published by. 15 Greek letters, forms, names, and English sounds of. 93 Ground-water features, symbols representing. 21-23 H. Hachuring, use of. 50 Half-tone engraving, preparation of copy for. 77-78 process and advantages of. 75-78 three-color process of. 78-80 Half tones, changes in. 39 prints of, showing effects produced by different screens. 56 requirements for printing. 11 Heliotype. _See_ Photogelatin processes. Hill shading, use of. 60-51 Hydrographic features, lettering of. 54 representation of. 51-52 Hypsographic features, lettering of. 54 I. Illustrations, kinds of. 10-11 Inks, kinds used. 25, 67 methods of using. 25 Inserting plates and figures, methods of, plate showing. 12 Instruments, draftsmen's, list of. 42 J. Japanese transparent water colors, use of. 26 L.