Читать книгу The Preparation of Illustrations for Reports of the United States Geological Survey - John L. Ridgway - Страница 3
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PREPARATION OF ILLUSTRATIONS PLATE I
METHODS OF INSERTING PLATES AND FIGURES.
1, 2, 3, 5, 6, 7, plates; 4, 8, 9, 10, figures; 11, pocket.
The illustrations will be finally divided into plates and figures when they are fully prepared, but if an author desires to determine the classification in advance of transmittal he should submit his material to the section of illustrations, where methods, processes, and reductions will be decided for each. In determining which shall be plates and which shall be figures, size and method of reproduction are the only factors to be considered; there are no other real differences. Illustrations that require separate or special printing, such as those reproduced by Lithography and by the photogravure, photogelatin, and three-color processes, must be printed separately from the text as plates and inserted in the report at the proper places; those that are reproduced by relief processes, such as zinc and copper etching and wax engraving, if not too large, can be printed with the text as figures. If an illustration to be reproduced by a relief process is marked for reduction to a size not exceeding that of the page of the text, it can be called a figure and be printed with the text. Half tones, though etched in relief, are rarely made text figures in Survey reports, because to give satisfactory impressions they must be printed on the best quality of coated paper, which is not used for the text. By using the coarser screens shown in Plate VI (p. 56), however, a half-tone cut may be made that can be used in the text if it is smaller than the page.
SIZES OF ILLUSTRATIONS.
The regular book publications of the Geological Survey are issued in three sizes—(1) octavo (annual reports of the Director, statistical reports on mineral resources, bulletins, and water-supply papers); (2) quarto (professional papers and monographs); (3) folio (geologic folios). The following table gives the measure of the text of each size and the measure of the trimmed page, in inches:
| Size of text. | Size of page. | ||||||||||
| Octavo | 4 | 3/8 | by | 7 | 15/16 | 5 | 7/8 | by | 9 | 1/8 | |
| Quarto | 6 | 1/16 | by | 9 | 1/8 | 9 | 1/4 | by | 11 | 5/8 | |
| Folio | 13 | 13/16 | by | 17 | 7/8 | 18 | 1/2 | by | 21 | 3/4 |
Most professional papers are printed in two columns of type, each 3 inches wide, and folios are printed in three columns, each 43/8 inches wide. A text figure in one of these publications can be made to fit one or more columns, and it may run the full length of the text page.
The limits of the dimensions of plates and figures, in inches, are given in the following table. If for any reason a plate can not be reduced to the dimensions of a page it can be folded once or more; and if it is large and unwieldy it may be placed in a pocket on the inside of the back cover. (See Pl. I.)
| Single-page plate. | Plate with one side fold. | Text figure. | ||||||||||||
| Octavo | 4 | 3/8 | by | 7 | 1/2 | 7 | 1/2 | by | 8 | 1/2 | 4 3/8 | by | 7 | 1/2 |
| Quarto | 6 | by | 9 | 9 | 1/2 | by | 14 | 3/4 | 3 or 6 | by | 8 | 1/2 | ||
| Folio | 15 | by | 17 | 1/2 | … … … … | 43/8 or 1313/16 | by | 17 | 7/8 |
For an octavo report a single-page plate with side title should be 4 inches or less in width, and a plate with bottom title should be 7 inches or less in depth. In other words, the actual depth and width of a single-page plate in a page of any size must depend on the number of lines in its title, the inclusion of which should not extend the matter much, if any, beyond the dimensions given in the table. A difference of 1 inch or less in the width of a folding plate may determine whether it must be folded once or twice, so that by consulting this table an author may save expense in binding and promote the reader's convenience in handling the plate.
A text figure (including the title) can not extend beyond the text measure but may be of any size or shape within that measure, as shown on Plate I, figures 4, 8, 9, 10.
SUBDIVISIONS OF PLATES AND FIGURES.
If a plate consists of two or more parts or photographs each part should be marked with an italic capital letter—A, B, etc.—which should be placed directly under each. If it is made up of many parts, in the form of plates that accompany reports on paleontology, each part should be similarly marked with an arable numeral—1, 2, 3, etc. If a text figure is subdivided into two or more parts, each part should be marked with a roman capital—A, B, C, etc.; and if details of a part are to be described each detail should be marked by an italic lower-case letter—a, 6, c, etc.
PREPARATION OF COPY BY AUTHORS.
CHARACTER OF ORIGINAL MATERIAL.
In the Geological Survey, as elsewhere, the "originals"—that is, the original material submitted by authors for the illustration of their reports—differ greatly in character and in degree of clearness. Some are carefully prepared; others are rough, obscure in part, and defective in detail. Drawings made from poor originals progress slowly, because the draftsman spends much time in interpreting uncertain features or in conference with the author concerning details. An original should be perfectly clear in detail and meaning, so that the draftsman can follow it without doubt. It should not consist of parts that must be brought together to make a new drawing, because the result of the combination of the parts will be uncertain at the outset and may not prove satisfactory. Each original illustration should be prepared with the idea that the draftsman who will make the finished drawing will be unfamiliar with the subject and will need definite instructions; all data should be plotted and each figure or plate should be completely made up before it is submitted. More or less roughly prepared originals are expected, but they should show no uncertainty in details. Obscure features may be cleared up by inclosing the features in penciled loops connected by a line with notes written on the margin, such as "omit this line," "turn at an angle of 30° from true north," "add," "cut out."
PRELIMINARY PREPARATION OF MAPS.
The base map that generally accompanies a report may be an original field sheet or it may have been compiled from various sources by an author and made to incorporate the results of his field work. It should not be a collection of maps of different scales and standards to be worked into a new map.
The source of the data shown on every original base map should be indicated on the map, whether it is to be used as an illustration or as a record of field work. This information is required as a permanent record for showing the reliability of the map, for use in comparing data, and for giving full credit to those who are responsible for the data. An author should see that this requirement is observed in order that proper credit may be given and should especially see that all cooperative agreements and organizations are properly mentioned.
An original map should preferably be complete in itself. It should not consist of several parts or sheets unless the data to be represented are unusually complex. All elaborate or technical finish of border lines, lettering, or like features should be left to the draftsman or the engraver.
Base maps that involve the compilation of new data should be prepared by either the topographic branch or the division of Alaskan mineral resources. If a base map already published is to be reused it should be submitted to the chief topographic engineer or to the chief of the division of Alaskan mineral resources for approval. This procedure will insure a single standard of geographic accuracy in maps appearing in Survey publications.
A geologist who requires a base map that includes new topographic data should address a request for its preparation to the chief geologist, who, through the Director, will refer the request to the topographic branch. The request must be accompanied by a full statement regarding the proposed report and the time when it is likely to be submitted. The preparation of such base maps by draftsmen in the division of geology, the land-classification board, the water-resources branch, or the section of illustrations has been discontinued except for the minor adaptations provided for above.
If a report requires the preparation of a base map that includes no new topographic data such a map must be compiled from other authentic maps by the division or branch in which the report originates. If, however, no draftsmen are available in that division or branch, an arrangement can be made with any other branch—as the topographic or publication branch—that may have draftsmen available, with the understanding that the cost of the work shall be reimbursed to the branch doing the work by the branch ordering it. For indicating geologic and other data, however, an author may make use of an authentic base map already published, and after it is reduced or enlarged to appropriate scale by photography such a map may suffice for transmittal with a manuscript.
MATERIAL AVAILABLE FOR BASE MAPS.
The maps already published by the Geological Survey[2] and other Government bureaus should always be consulted when a new base is to be compiled. The following list includes most of the maps available:
1. The Survey's regular topographic atlas sheets, published on three scales—15-minute sheets, scale, 1:62,500; 30-minute sheets, scale, 1:125,000; 60-minute sheets, scale, 1:250,000—approximately 1 mile, 2 miles, and 4 miles to 1 inch, respectively—and its "special" maps,[2] some of which are published on other scales. All these maps can be used as bases for detailed geologic maps, for compiling maps on smaller scales, and for revising other maps.
2. The United States part of the international map of the world, now being published on the scale of 1:1,000,000 (approximately 16 miles to 1 inch). Each sheet of this map represents an area measuring 6° of longitude and 4° of latitude. The published sheets of this map may be used as bases for general maps. The sheets are drawn on the scale of 1:500,000, and photolithographs on this scale are available for use as bases for geologic or other maps.
The adaptability of the 1:1,000,000 scale map to use as a base for general geologic maps is shown in the geologic maps of the southern peninsula of Michigan and of Indiana in Monograph 53 (Pls. IV and VII), the map of Florida in Bulletin 60 (Pl. I), and the map of Vermont in Water-Supply Paper 424 (Pl. I).
3. The Survey's two-sheet wall map of the United States, 49 by 76 inches, scale 1:2,500,000 (approximately 40 miles to 1 inch). Parts of this map can be used as bases for general geologic or other maps and as copy for index and other small diagrammatic maps. This map is published both with and without contours.
4. Land Office maps and township plats. These maps are now being published on a scale of 12 miles to 1 inch; they are also photo-lithographed on one-half that scale, or 24 miles to 1 inch. The township plats are printed on a scale of one-half mile to 1 inch. The maps are especially useful in compiling maps in which land lines (townships and sections) are essential, and the township plats afford valuable detail and are useful in field work and in revising other maps. Township and section lines should appear on all land-classification maps published by the Survey. On maps on a scale less than 1:250,000 only the townships should be shown; on maps on scales greater than 1:250,000 the sections should be shown; on maps on a scale of 1:250,000 the sections should be shown, unless their representation will materially impair the legibility of the map, in which case only the townships should be shown. (See fig. 1.)
5. Post-route maps, covering single States or groups of adjacent States, published on sheets of different sizes and on scales determined mainly by the size of the State. The map of Texas is published on a scale of 12 miles to 1 inch, that of Virginia on a scale of 7 miles to 1 inch, and that of West Virginia on a scale of 6 miles to 1 inch. Both the Land Office and the post-route maps are useful for reference in compiling maps on smaller scales. Post-route maps are especially useful for comparing and verifying the location of cities, towns, and railroads.
6. Coast and Geodetic Survey charts, published on scales that are governed by the area represented and the amount of detail to be shown. These maps should always be used in compiling and correcting coast lines.
7. Maps and charts published by the Corps of Engineers of the Army, the Mississippi River Commission, the surveys of the Great Lakes, and the boundary surveys. These maps are especially useful if the scale of the map to be compiled requires considerable detail.
8. The Survey's three small base maps of the United States—(a) a map 18 by 28 inches, scale 110 miles to 1 inch, which is published both with and without contours, or with relief or hypsometric shading; (b) a map 11 by 16 inches, scale 190 miles to 1 inch; (c) a map 71/2 by 12 inches, scale 260 miles to 1 inch, designed for use as a two-page illustration in a bulletin or a water-supply paper.
9. The Century, Rand McNally & Co.'s, Cram's, Stieler's, The Times, Johnston's Royal, and county atlases.
10. State and county maps.
11. Railroad surveys, which are useful in furnishing data for elevations as well as for locations of towns and stations.
12. The latest national-forest maps and proclamations. It is, however, not necessary that national forests, bird reservations, and national monuments be shown on a map in a report unless their addition is specially requested by the author or by the chief of the branch submitting the report, and they should not be shown if they will obscure other more important data.
[2] See "Topographic maps and folios and geologic folios published by the United States Geological Survey" (latest edition).
Figure 1.—Diagrams showing principal, guide, and auxiliary meridians, standard and special parallels and correction lines, and system of numbering townships, ranges, and sections.
The Survey has published numerous maps of parts of Alaska, as well as other maps, which are available for use or reuse in its reports. Copies of all base maps for which copper plates have been engraved by the Survey can be obtained on requisition, and their use in a new report will save time as well as the cost of engraving. Other maps will be found in the Survey library, where the latest editions only should be consulted.
BASIC FEATURES OF MAPS.
It must be remembered that "every map, whatever its scale, is a reduction from nature and consequently must be more or less generalized."[3] The degree of generalization in the geologic and other detail to be shown on a map usually involves a corresponding degree of generalization in its base. Absolutely true generalization means the same degree of omission of detail for each kind of feature. If a base map on a scale of 1 mile to 1 inch, prepared with the usual detail, were placed before a camera and reduced to a scale of 16 miles to 1 inch, the lines representing the smaller tributaries of streams and the smaller water bodies, as well as many other features, would probably be so greatly reduced in length as to be illegible. If from this reduced photograph a new map were prepared, from which all features not plainly discernible were omitted, the new map should represent what might be called true generalization. This degree of generalization is, however, not practicable, but unessential detail should be systematically omitted. The amount of detail which a base map should show is limited by its scale, by the character of the country it represents, and by the kind of data to be shown. Coordinate features of a topographic map should be shown with equal detail. Detail in culture may call for detail in drainage, though relief may be greatly generalized or entirely omitted; detail in relief may like-wise call for detail in drainage, though culture may be more generalized.
[3] Gannett, Henry, A manual of topographic methods: U. S. Geol. Survey Mon. 22, p. 107, 1893.
If the three fundamental features of a topographic map—the culture, the drainage, and the relief—are to be engraved or photo-lithographed separately and printed in colors, the best results can be obtained by drawing each feature in a separate color on one sheet unless the work is coarse and great precision in register is not needed. The culture should be drawn in black waterproof ink, the drainage in Prussian blue, and the relief in burnt sienna; but care should be taken that the colors used will photograph well. To insure a good photograph it is usually necessary to add a little black to the blue and brown. (See "Inks," p. 25.) The photographer will then make three negatives and will opaque or paint out all but one of the three features on each negative. The cost is somewhat greater than that of reproducing three separate drawings, but the result gives more accurate register than if the drawings were made on separate sheets, which are likely to change in size before they are reproduced.
STANDARD SCALES.
The standard scales of the maps used in the publications of the Geological Survey are fractions or multiples of 1:1,000,000 (see p. 14), except for a map that is reduced expressly to fit one or two pages of a report or that is reduced horizontally or vertically to fit the text as a small diagrammatic or index map. It should be remembered that a map which may be serviceable for use in compiling a new map, except as to scale, can be reduced or enlarged to the scale of the new drawing by photography, by a pantograph, or by other means. (See p. 47.)
Maps compiled by an author should be prepared on a scale of at least 11/2 times and preferably twice the size of the scale used on the published map. Maps traced on linen should be no less than twice the size of publication. Not only is the quality of the reproduction improved by considerable reduction, but the larger scale of the drawing facilitates the plotting of details. It should be remembered, however, that a linear reduction of one-half produces a map only one-fourth the area of the original, and reduction so great may prevent the addition of data, such as an extended note in small letters applying to a small area on the face of a map, which would not be legible when reduced.
ORIENTATION OF MAPS.
A map that bears no arrow indicating north is supposed to be oriented north and south, and its title should read from west to east. If, however, the area mapped has a general trend in one direction, as northwest to southeast, and its squaring up by a north-south line would leave too much blank paper, this general rule is not followed. The border lines on such a map should conform to the general trend of the area mapped, an arrow should show north, and the title and scale should be placed horizontally, but the projection numbers and town names should follow the direction of the parallels of latitude. (See Pls. X and XII, Bull. 628; and Pls. VI, XV, and XVI, Mon. 52.)
PROJECTION.[4]
[4] See also pp. 43–45, where the method of projecting a map is more fully explained.
The polyconic projection has been adopted by the Geological Survey for its topographic atlas sheets and must be consistently used for its other maps. If a new map is to be compiled an accurate projection should first be constructed, and no plotting should be done on it until the projection has been checked and found to be correct. A projection should be checked or proved by some one other than the person who prepared it. Next the drainage and the water areas should be outlined; then the cultural features should be added; and finally the relief, whether expressed by contour lines, hachures, or shading.[5]
[5] See pp. 49–48 for methods of tracing and transferring.
EXPLANATION.
Under the heading "Explanation" should be placed all matter needed to describe fully the details of an illustration, whether map, diagram, or section, so that if the illustration became detached it would be a complete self-explanatory unit.
The explanation of a map may be placed inside the border lines if there is ample room for it, or it may be placed outside. The standard arrangement for an outside explanation for geologic maps is shown, in the geologic folios, which should be followed in general form. If there is space within the border lines the explanation may be appropriately arranged therein, either in a vertical column or horizontally, according to the size and shape of the space available. If the sequence of formation is shown by horizontal arrangement the younger formations are placed at the left and the older at the right. If it is shown by a vertical arrangement the youngest formation is placed at the top.
Each original map submitted by an author should have at least 41/2 inches of blank margin on the right and at the bottom in which to place the explanation, scale, title, and other matter, but the author should make no attempt to elaborate these features nor should he employ a draftsman to letter them carefully. Plainly written ordinary script is quits sufficient for original maps; the final lettering, which may consist entirely of impressions from type, will be added after submittal of a report.
TITLES OF MAPS AND OTHER ILLUSTRATIONS.
The titles of maps should be supplied by authors but are subject to revision in order to make them agree with established forms. They should be written in ordinary script, not carefully lettered. They should state concisely the kind of map, the area shown, the special features represented, and the county, State, or Territory in which the area is located. (See p. 58.) Titles are reproduced directly only on lithographs, three-color prints, photogelatin plates, and other illustrations that are printed by contractors, not by the Government Printing Office. The titles of illustrations that are repro duced by relief processes, such as zinc etching, half tone, and wax engraving, are printed at the Government Printing Office from type, and proofs are submitted to the authors for examination.
SYMBOLS USED ON MAPS.
GENERAL FEATURES.
More than 200 symbols have been used on maps to express 25 different kinds of data, a fact indicating at once a notable lack of uniformity and a need of standardization. It is of course impossible to provide a characteristic symbol that can be used uniformly for each kind of feature, and therefore the same symbol may be used on different maps to express different things. The symbols shown in Plate II are those most used on geologic maps. The symbols for dip and strike, fault lines, mine shafts, prospects, and several others are generally well known, but on some maps it may be necessary to modify a standard symbol to express additional distinctions. The symbols shown, however, will cover all the ordinary requirements of miscellaneous mapping. Though the plate shows more than one symbol for some features the symbol most commonly used is given first and should be preferred. The center of each symbol should mark the location of the feature symbolized. Symbols are not always platted with sufficient care. On small-scale maps they are difficult to locate and unless great care is taken in platting them they are likely to be several miles out of place. All symbols should be located precisely where they belong.
The symbol showing dip and strike should be accurately platted by means of a protractor, so that the strike will be shown graphically, without a number and a degree mark, and not need replatting by a draftsman or engraver. The dip, however, should be indicated by a number and a degree mark.
LETTER SYMBOLS.
The letter symbols used on most geologic maps to indicate the ages and names of the formations represented consist of two or more letters—an initial capital letter for the name of the system and one or more lower-case letters for the name of the formation or of the material, as Qt (Quaternary—lower terrace deposits); Cpv (Carboniferous—Pottsville formation); COk (Cambrian-Ordovician—Knox dolomite), etc. The standard usage for this feature is shown in the geologic folios but is subject to modification in other publications.
In preparing an original geologic map a letter symbol, such as has been just described, or a number should be put in the proper place in the explanation, and the same symbol or number should be repeated at one or more places on the map within the areas to which it refers. Each area that is indicated by a color should be marked with the proper symbol in order to make its identification sure, for light colors especially are likely to fade and mixed colors can not be discriminated with certainty.
U. S. GEOLOGICAL SURVEY
PREPARATION OF ILLUSTRATIONS PLATE II
SYMBOLS USED ON GEOLOGIC MAPS, ECONOMIC MAPS AND MINE PLANS
OIL AND GAS SYMBOLS.
A complete set of symbols for maps showing oil and gas is given on Plate II. Referring to these symbols the chief geologist, in a memorandum to the Director, writes:
The symbols used by the Survey in its oil and gas maps have not been in accord with those used by the oil companies, nor have they been wholly logical. It appears that though they were submitted for recommendation they never have been formally approved.
Herewith I submit a code prepared by the geologists of the oil and gas section. They conform largely to commercial use and embrace its best features as well as the best and most logical features of our previous usage, the departures from which are, after all, of minor consequence.
The symbols here submitted [see PI. II] with recommendation for approval are founded on a building-up system, so that the history and the results of drilling at any location can be recorded by slight additions to symbol and without erasure. Thus maps may be revised without scratching.
In drawing these symbols the draftsman should make the rays of the gas well distinct and in adding the vertical bar or line showing that a hole is dry or abandoned should make it long enough to be distinct. It would be preferable to draw this bar obliquely, but an oblique position would coincide with some of the patterns on certain maps, and it should therefore be placed vertically. The vertical line indicates the failure or abandonment of the well, the symbol for which Is thus scratched off or canceled by the line drawn through it. The symbols agree so far with commercial usage that oil men will have little need to consult the explanation.
SYMBOLS FOR USE ON MAPS SHOWING FEATURES OF GROUND WATER.
The symbols used on maps relating to ground water represent the features named below, each of which has been shown in publications already issued.
| Area of absorption or outcrop. Depth to water table. Contours of water table. Fluctuation of water table. Depth to water-bearing formation. Structure contours of water-bearing formation. Area of artesian flow. Head of artesian water. | Area that discharges ground water. Quality of ground water. Area irrigated with ground water. Nonflowing well. Flowing well. Unsuccessful or dry well. Well with pumping plant. Spring. |
The lack of uniformity in the symbols commonly employed to represent these features is due to differences in the number of color on the maps and differences in the scale. Standard colors for the larger features, such as those for areas of artesian flow, areas of absorption, and curves showing depths to water table or to water-bearing formations, can not be fixed, because of considerations of economy in printing. For example, if light green is the standard color to be used for delineating areas irrigated by ground water and no green is used on other parts of the map its use would represent an additional or special printing, whereas a tint of blue, brown, or purple, if any of these colors is used for other features on the map, might be used also for this feature without additional printing. Therefore the general use of any particular color for a water feature seems to be impracticable; but this fact should not preclude the adoption of color standards for use subject to the requirements of economy in publication.
The ordinary symbols for wells are the open circle and the solid circle, or dot. Only in the secondary or specific well symbols does there appear to be lack of uniformity, the choice of secondary symbols being governed either by personal preference or by the requirements for specific distinction.
All symbols should, if possible, suggest the things they represent. Wells are circular and hence the open circle is most used and most appropriate for nonflowing wells. To indicate a flowing well the circle is made solid, denoting that the well is full of water. For an unsuccessful well the most suggestive symbol would be an open circle with a line drawn through it to denote cancellation. It has been suggested that if water features, including wells, are to be printed in blue, unsuccessful wells, or dry holes, be printed in black. A large circle drawn around the symbol for a flowing or nonflowing well will appropriately denote a pumping plant at the well.
The accepted symbol for a spring is a dot with a waved tail representing the direction of flow, if known. This symbol can not be modified without destroying its prime characteristics, but it may be accompanied by a letter indicating the kind of spring. An open circle with a tail might be used on large-scale maps, but it would be out of scale on other maps, whereas the black or blue dot and tail will fit maps of any scale.
The following colors and symbols can most appropriately be used to represent ground-water features. The well and spring symbols can be varied by adding letters if they are necessary to express other data than those indicated in the list below.
General ground-water features.
Area of absorption or outcrop: Flat color used on the map to show the geologic system in which the absorbing formation occurs.
Areas showing depths to water table: Shades of purple and gray; if possible the shades showing the areas of least depth should be darkest and the shades should grade from those to lighter tints.
Contours of water table, or contours on water-bearing formations: Gray or purple curves or lines.
Areas of artesian flow: Blue flat tint, or fine ruling in blue. Depth to water-bearing formations: Gradation of a single color or of two related colors from dark for shallow depths to light for greater depths.
Nonflowing artesian areas (pumped wells): Green flat tint, or fine ruling in green. Depth to water-bearing formations shown by gradation of tint if possible from dark for shallow depths to light for greater depths.
Head of artesian water: Blue curves or lines.
Areas that discharge ground water: Blue flat tint, or fine ruling in blue.
Areas irrigated with ground water: Green flat tint, or fine ruling in green.
Well, character not indicated.
Well, nonflowing.
Well, flowing.
Well, unsuccessful or dry.
Well, nonflowing, with pumping plant.
Well, flowing, with pumping plant.
Springs.
Spring, thermal.
Spring, mineral.
The standard color scheme should be used if no conditions preclude its use, but if other colors can be used with greater economy without sacrificing clearness the use of the standard colors should be waived.
BLACK-LINE CONVENTIONS.
A complete set of the black-line patterns used to distinguish areas on a map is given in Plate VIII (p. 60), and their application to a finished drawing is shown in figure 9 (p. 62). These patterns, however, should preferably not be used by the author in his preliminary work on an illustration. For this purpose water colors or colored crayons are preferable, and the distinctions between areas may be emphasized by letter symbols.
MATERIALS USED IN PREPARING MAPS.
PAPER.
For large and important maps which may at some time be extended to cover a greater area or which may be made to fit maps already prepared or published the paper used should be mounted on muslin to reduce to a minimum the shrinking or stretching caused by atmospheric changes. Pure white paper produces a better negative than a cream or yellowish paper and will retain its color longer, but all papers become more yellow with age and exposure to light.
The following brands of paper are used in the Survey in the preparation of maps:
"Normal" K. & E., unmounted. Has an excellent surface and comes in flat sheets, 19 by 24, 22 by 30, and 27 by 40 inches.
"Paragon" K. & E., mounted on muslin. In 10-yard rolls 72 inches wide. Used in the Survey for large office drawings and maps of large scale.
"Anvil" K. & E., mounted on muslin. In 10-yard rolls 42, 62, and 72 inches wide. Used in the Survey for large drawings.
"Whatman's hot pressed," unmounted or mounted on muslin. In sheets ranging in size from 13 by 17 to 31 by 53 inches. An excellent paper for maps. The muslin-backed paper is recommended for use in preparing large detailed maps and base maps that are to be retained as permanent records. The muslin provides a durable and flexible backing that permits the map to be rolled, and paper thus mounted is particularly serviceable for a map which may be subjected to considerable revision and to which must be added finally a title, explanation, and other marginal matter.
"Ross's relief hand-stipple drawing paper." A stiff enameled or chalk-coated paper whose surface has been compressed into minute points that stand in slight relief so that a shade made on it with pencil or crayon is broken up into dots and can be reproduced by photo-engraving. For use in making shaded drawings, drawings showing relief by light and shade, etc. Similar paper is prepared for parallel-line and other pattern effects. In sheets ranging in size from 11 by 14 to 22 by 28 inches. (See p. 51 for method of using.)
Profile and cross-section paper. In sheets of convenient sizes or in rolls. Bears lines printed in blue, green, red, or orange, in many kinds of rulings, which may be selected by reference to catalogues. Profile and cross-section paper printed in orange is recommended for preliminary drawings; blue is recommended for drawings that are made in pencil and submitted for inking in.
BRISTOL BOARD.
For the smaller maps, such as key maps and maps less than 18 by 24 inches, and for small drawings made for direct reproduction, Reynolds's bristol board is recommended on account of its pure-white color and its hardness, which permits erasures to be made without affecting redrawing over the corrected area. It is obtained in 2-ply, 3-ply, and 4-ply sheets. The 2-ply and 3-ply are especially useful in making delicate brush and pencil drawings and pen and ink drawings. The sizes used in the Survey are 161/2 by 203/4, 181/4 by 223/8, and 211/2 by 283/4 inches.
TRACING LINEN.
Tracing cloth or linen is especially useful for large work that will require considerable reduction. (See p. 18.) Its advantages are that a tracing that has been carefully made on it over any kind of copy for direct reproduction by a photo-engraving process can be used for making a paper negative for contact printing or blue printing. On the other hand, it is susceptible to atmospheric changes that affect scale, and the lines traced on it are not reproduced as sharply as those made on paper. It can be obtained in rolls 30 to 54 inches wide.
Erasures should be made on tracing linen with a hard rubber eraser, not with a sand rubber or a steel eraser.
INKS.
The best drawing inks are in liquid form, ready for use. They should be waterproof and equal to the grade known as Higgins's waterproof ink. When a suitable waterproof blue ink can not be obtained, a good blue for features of drainage can be made by dissolving a half pan of Winsor & Newton's prussian blue in water. No good waterproof burnt sienna ink seems to be obtainable, but a good substitute can be made by dissolving Winsor & Newton's water color of that name.
Ink lines should be drawn in full strength of color—lines that should be black must not appear grayish, for example—and pens should be kept clean. The same pen should not be used for applying two inks, as the mixture thus produced is likely to thicken or coagulate on the pen. A little black should be added to colored inks that are used in making drawings to be reproduced in colors in order to strengthen the lines for photographic reproduction.
DRAWING PENS.
The pens made by Keuffel & Esser, especially their No. 3202, and Gillott's Nos. 291, 290, 170, and 303 give complete satisfaction. The Gillott numbers are given in the order of fineness of the points. No. 291 being the finest. The best cleaner for a drawing pen is a piece of chamois skin.
PENCILS.
Pencils used for drawing should have leads of a quality equal to those of the Koh-i-noor brand, in which the grades of hardness are indicated by 3B, 2B, B, HB, F, H, 2H, 3H, 4H, 5H, 6H, 7H, 8H, and 9H; the softest grade is 3B and the hardest 9H. The grades most generally used are B, HB, F, 4H, and 6H.
RUBBER ERASERS AND CLEANERS.
Two kinds of rubber erasers are usually employed in making erasures on drawings—a hard, dense rubber like the "Ruby," and a soft, pliable rubber like the "Venus" or "H" (Hardtmuth). The soft rubber is also useful for cleaning large surfaces. Art gum is also recommended for this purpose and has the advantage of not disturbing the surface of the paper.
COLORED PENCILS AND CRAYONS.
Colored pencils and crayons are useful only for coloring preliminary maps. They are not recommended for use on maps that are to be kept for reference or to be submitted for reproduction, because the colors rub off, but they can be used on photographic prints of base maps or on transparent oversheets, for which the unglazed side of tracing cloth is well suited. When they are so used register marks should be added at numerous points on the map and the oversheet, including the four comers, the color boundaries should be drawn or traced, and finally the colors should be added. Two or more colors should not be used on any one area to modify a tone, but each area should be colored with a separate crayon. Patterns or designs should not be used except to strengthen contrasts, and for that purpose a pattern may be drawn with a black pencil over a color.
WATER COLORS.
By dilution to half strength some of the standard water colors will yield a tint or hue that will contrast with other tints or hues produced in the same way quits as well as undiluted or full colors will contrast with one another. The colors named below, except chrome-yellow and emerald-green, are among those that when diluted will afford satisfactory contrasts among themselves and with their full colors and are recommended for use in coloring original maps.
| Mauve. Crimson lake. Orange-vermilion. Burnt sienna. Cadmium-yellow. Chrome-yellow. Olive-green. | Hooker's green No. 2. Emerald-green. Payne's gray. Lampblack. Sepia. Cerulean blue. |
Other pigments spread better than cerulean blue and emerald-green, but the exceptional purity of color of these two seems to warrant their use.
JAPANESE TRANSPARENT WATER COLORS.
Japanese transparent water colors, so called, are used by some geologists. They spread evenly and are convenient for field use, but they can not be washed out like other water colors, so that when they are once applied to an area and a change of color becomes necessary they must be bleached out. A good bleach is sodium hypochlorite, which should be applied with a brush until the color disappears, and the area dried with a blotter before recoloring. Light tints of these colors are believed to be somewhat fugitive if exposed to strong light.
COLORING GEOLOGIC MAPS.
The colors used on most original maps are not pleasing, a fact that is of no particular importance, but—and this is of importance—they often fail to give clear distinctions; the separate areas can not always be identified or distinguished with certainty. Again, some colors are fugitive, and when laid on in light tints they disappear entirely or become uncertain. Much of the difficulty in identifying and discriminating colors on an author's original maps is due to the promiscuous mixing of colors. Many persons can not match or discriminate mixed or broken colors. Hence if the supply of a color produced by mixing becomes exhausted and the attempt is made to duplicate it by a second mixture the two will probably fail to match. It is therefore suggested that colors in full strength and colors diluted to half strength be used instead of mixtures of two or more pigments, so that one color in two strengths or tones can be employed to indicate areas that are to be distinguished. The colors listed on page 26 will give 24 satisfactory distinctions and will thus supply all demands for map coloring.
To insure satisfactory contrasts between colored areas on a map, unlike colors should be placed next to each other—that is, colors should be placed together that are widely separated in the spectrum, such as yellow and mauve, red and green, blue and orange, burnt sienna and olive-green; not such as red and orange, blue and purple, orange and yellow, sepia and burnt sienna.
A sufficient quantity of water and color pigment to be used for one formation area on a map should be stirred in a saucer until the desired tint is produced before it is applied. To maintain the same tone properly the color should be well stirred every time the brush is filled; if it is not stirred the brush will on the next dipping take up a lighter tint, because most pigments, especially those derived from minerals, tend to precipitate. When the colors are applied the map should preferably be placed in a slightly inclined position, and the coloring should be started at the upper boundaries of an area to be colored, the well-filled brush being pulled toward the painter and Worked rapidly back and forth horizontally, the edges of the fresh color being kept wet. If the edges are allowed to dry, a hard line and a smeared or uneven effect will be produced.
A strong color should generally be used for small areas unless the map shows also large areas that must have the same color; lighter hues should be used for large areas. Bright colors are best suited for areas of igneous rocks, dikes, and veins, and these may be reduced in strength for the larger areas.
The Survey's color scheme (see p. 63) need not be applied at this stage of preparation, except in the most general way. Appropriate final colors can be best selected when the new map is made ready for engraving. In the author's original maps adequate color distinctions between areas are more important than the use of standard geologic colors. Patterns should not be ruled in one color on an original map to indicate distinctions between different formations of the same age or period, because such patterns are difficult to produce by hand with proper uniformity except by engraving.
It is of vital importance that an original base map should be free from colors and from technical symbols in order that it may be kept clean for photographing and preserved for possible future use. Such a map should preferably be photographed in order to obtain prints on which to add the colors and symbols; the use of an oversheet for this purpose is not nearly so satisfactory. When photographed a base map should be reduced to publication scale in order to save the additional cost of a larger negative, and this reduced map may be made up for publication by the addition of colors and symbols, title, explanation, etc.; but the lithographer will also need the original base map from which to make his reproduction.
DIAGRAMS.
ESSENTIAL FEATURES.
The term "diagrams," as used here, includes such illustrations as mine plans, profiles, sections, stereograms, and maps that are more diagrammatic than cartographic. The first essential in the original drawings for simple diagrams is clearness of copy. Simplicity of subject does not warrant hasty preparation, for an original sketch that has been carelessly drawn and is inaccurate or inconsistent in detail may lead to serious errors. Ruled paper printed especially for platting profiles and cross sections should be used. Curves or graphs made by an author with pencil on blue-lined section paper may be inked by more skillful draftsmen. An author's pencil sketches are usually satisfactory if they indicate plainly the facts to be represented, but they should be prepared with some care as to detail. Tables and like matter are not generally satisfactory material from which to prepare drawings. In drawings for diagrams that are to be printed in the text as figures the use of large, solid black bars or of conspicuous areas of solid black is objectionable, because the black is likely to print gray and to appear uneven in tone. Ruled tints or cross lining give better effects. Stereograms should be prepared by an author with especial care, for they represent facts only as the author sees them, and the author's view must be imparted to the draftsman graphically. The "third dimension"—the relief—in such drawings is not easily expressed and should be brought out clearly in the author's rough sketches.
For illustrations of apparatus photographs are preferred, but if rough sketches are submitted they should show not only correct relations but all dimensions.
PLANS OF MINE WORKINGS.
Blue prints obtained from mining companies are acceptable for plans of mines or underground workings, but all unnecessary or irrelevant details on such plans must be canceled and all essential features retained, and every essential feature, especially any added data, must be clearly interpretable. Many such blue prints are so large and unwieldy that they must be greatly reduced by photography before they can be redrawn. If the lines are too weak to photograph, a tracing of the essential parts can be made and reduced to about twice publication size. The shadowless drafting table, described on pages 47–48, is well adapted to the work of making such tracings. Blue prints can also be pantographed to any convenient size if the details are not too minute or complex.
